This page covers replacement of valve cover seals, fuel injectors, and intake manifold gaskets. While you have the manifold off, it is easy to replace the rear spark plugs, and the oxygen sensor.
I write this for people of limited resources and experience, so include some just-good-practice items.(This is yet another job impeded by Chrysler's sloppy design of engine installation connections.)

Suggested tools:
- 3/8" drive ratchet wrench, short and medium length extensions for it, and short 13mm socket
(optionally a ratcheting closed end wrench, 13mm) - standard spark plug socket (regular size 13/16", no swivel)
- spark plug wire puller - short to medium extension bar (clearance to firewall is a bit tight, normal medium extension is 3" but a 2" would be better - perhaps the combination of a 3/8 to 1/4 and 1/4 to 3/8 adapter would work), but wrench space will be tight and you'll need an experienced touch to start threading the replacement plug in correctly.
- thumb turn wheel that fits in place of ratchet wrench, for feel installing plugs and for quicker turning
- air supply with nozzle (to blow junk out of spark plug well)
- low profile ratchet (1/4" drive), short and long extension bars, swivel joint adapter (wrap tape around it to limit movement, alternatively a 10mm socket with integral swivel might work), and 10mm short rigid socket. Desirably with a magnet to hold the bolts so they don't fall down somewhere.
- gasket scrapers
- foam or paper towel to stuff into openings to prevent scrapings from falling in
- clean oil to apply to the new injector o-rings if you pull them out.
- 3/4" deep socket for the coolant temperature sensor if you remove the lower manifold (to get it clear of bolt once loosened)
- magnet to hold the EGR tub plate up on the tube
- mirror to see the EGR tube plate bolts
- sealant, very high temperature, to use for the EGR tube plate after you lose the second gasket (well, actually, see the precaution below)
Let the engine cool down before working on the rear plugs and bolts, as you'll be touching the exhaust manifold.

Parts:
There are lower and upper intake manifolds in the 3.3L engine. (Whereas the manual refers to the visible one of the 3.0L engine as "plenum".)
You can see the upper manifold with its individual cylinder runners and let out to the throttle body. The fibre gasket under that is shown by service manual Section 11 Figure 13, handling all six square ports. It has four bolts. Below that nestled between the cylinder heads is a set of runners in a casting that attaches to cylinder heads with bolts, each head having three rectangular ports plus rectangular coolant holes (see Figure 14 of Section 11). A metal gasket gasket is used below that manifold, with special sealing at the ends of the flat lower part of the vee. - The injectors push into the lower manifold, you can just see the output end of each. They are held in place by the fuel rail.
- FelPro's gasket set includes both manifold gaskets plus the EGR tube gasket, sealant, and o-rings for both ends of the injectors. While Chrysler's IPC lists different part numbers for the o-rings for 3.3L versus 3.8L engines, FelPro's kit covers both.
- A spare gasket for the EGR tube as you may lose the first one (well, actually, see the precaution below)
- Be very careful with the clips holding the injector to the fuel rail, people have broken them, they are very difficult to find with the stabilizer prongs on, and expensive. (P/B ????? appears to fit, no prongs, just as expensive though.)
- Wire loom protection material, as the original corrugated material will be falling apart. 3/8" should do most looms you'll expose, with effort and cleverness you can get it through the clamps that hold the loom to things for support. Medium temperature type is preferred.
Long twist ties, as the attaching prongs of some of those clamps may have fallen apart (zip ties may be best due finger access below the throttle cable bracket, I had to tie the twist ties rather than twist them).

REMOVING UPPER INTAKE MANIFOLD
> drain coolant (as you'll have to remove coolant temp sensor, and besides you don't want coolant leaking into cylinders when head bolts are loose, some of the upper manifold bolts also retain the lower manifold which contains the sensor and has coolant passanges into heads)
> detach ignition coil and tie it up to the side
> remove bolt holding fuel lines, to give some room for movement to lift the fuel rails up and forward, oh go ahead and disconnect the fuel lines.
> a slim extension bar and a swivel joint adapter are best for the aft as the bar tends to bind on manifold runners
> you should be able to remove only the one bolt of the alternator bracket, without releasing belt tension, BUT it will be very awkward to get the aft right valve cover bolt in without cross-threading.
> there are many wires and vacuum lines, including ground strap at aft right (bolt also holds plug wire retainer), small vacuum lines under the throttle-body to manifold runner, large vacuum line to brake booster (hose clamps are a pit especially if you don't have a hose clamp pliers, but the hose pulls off relatively easily once you have the clamp tabs squeezed), breather hose (remove it from the valve cover grommet to improve clearance to remove valve cover), several sensor connectors around the throttle body and at the back of the manifold. Be careful with the small black vacuum lines as they are brittle.
> detaching the EGR pipe from the throttle body is a pita, best from the front to the right of the manifold (left when facing it), 13 mm socket or 13 mm closed end racheting wrench, the tricky aspect is getting them square on the bolt heads while having clearance to swing (note orientation from the front view, two bolts up through a plate).
> the service manual shows a brace from the aft cylinder head to the aft left corner of the main part of the manifold.
> throttle cables detach by moving the throttle bellcrank by hand, lifting cable ends aft and sliding the cylindrical keeper inboard. Then unbolt the cable bracket from the throttle body.
> Beware that when re-installing the upper manifold, you'll need to get the EGR tube attached before tightening the manifold down, you need to get the gasket centre hole over the end of the tube. I suggest doing that first so it slides down to the plate and doesn't get lost, rather than holding it against the throttle body. Holding the plate up with a magnet below it on the tube is helpful. If tube and throttle body don't line up, beware that viewing angle can mislead you, and that there's slop in holes (once you've got screws in the plate, wiggle the tube around to help centre it).