TPS replaced, still acting weird

I know jack about cars. I bought a 96 Galant from my sister after the tranny went in it. She put a rebuilt tranny in it and sold it to me. Heres what it is doing:

After warming up (10 15 mins of driving), and at around 30-40 mph, its starts hiccuping and the rpms bounce between 2-3000. Once you get past 50 it is fine.

When you go to stop, the thing vibrates like crazy, the oil light flickers on, and on some occasions it stalls.

We replaced the TPS sensor (computer had weird readings on it) And that did not do a thing. Took it to the tranny shop where it was rebuilt. Guy says the fuild is nice and red and there is nothing wrong with the tranny.

It does this in OD and out of it. Any clues? :screwy: :banghead: :banghead:

Been reading back on some past posts and am noticing that they don't get a lot of replies. The replies on trannys are usually "Take it to a specialized tranny shop and have them diagnose it." Although I intend on doing this very thing, I want to get a heads up on what it MAY be. I've been burned many times on getting something replaced that didn't need to be or paying way more then I needed to, so I was hoping I could get a response to this by the end of the weekend.

OK, guess I am not getting any help on this!
Thanks for nothing