The solenoid pack and computer is probably fine. Good since they cost $$$.
I rebuilt the tranny in both our Mopar minivans about 2 years ago. The 96 Voyager 4 cyl 413 is called a Torqueflite and almost identical inside to a 904 or 727. It was flaring between 1st and 2nd. The clutch plates were totally worn down w/ the fingers almost gone, and an output bearing worn up. Most was due to a bad rebuild by a big shop (Certified Transmission label, I bought from JY). They inserted an extra steel plate so they could re-use worn clutch plates, and left off the screw retainers on the output shaft, so the screws backed off and the bearing failed.
I think all V-6 minivans got the 604 electronic 4-spd tranny, which was in my 02 T&C. I only rebuilt mine because I had it off to replace a cracked flexplate, and didn't know its history. It was so perfect inside that I re-used the clutch plates (<2 mil worn) and only replaced rubber seals. It was simpler inside than the Torqueflite. It has no bands. They cleverly use extra clutch packs to the outer case to lock the drums. I stopped at the L/R clutch pack and left the over-running clutch and output bearings in place, which keeps things simple. If everything feels tight and smooth, you can do the same. Keep the bell-housing pointed up so that stuff stays put in the bottom. Putting those clutch rollers and springs back is tricky.
I suggest buying the ~$80 "banner kit", which doesn't include steel plates. You can buy separately if yours are too worn (unlikely, but mic them). You might also get the tri-metal bushings that go between clutch packs and aren't in many kits. Also look into an after-market "pin retainer" for the differential. If you spin a front tire on ice, the centrifugal force can throw the set-screwed gear pin out thru the case. Maybe that is just on 413 and earlier trannys. I didn't get into the differential in my 604. I bought the factory manual for the 604, which is very detailed step-by-step, with many figures. Makes it hard to mess up. The only special tools needed was long snap-ring pliers. For the 413, I found a manual free online, via a Neon tuner website.