1987 Caprice Classic

I am working on a 87 caprice with a thm200-4r transmission. Ill start out by saying I replaced this transmission for a friend a few years ago and the car did just fine however one day he said he pulled in his driveway and fluid was pouring out from what he seemed to explain the front seal.  Being that he isn’t the brightest crayon in the bow when it comes to cars he continued to let it run.  Afterwards he had someone else remove the pan and im very positive it wasn’t a experienced mechanic but they said there was metal all in the pan “not sure if it was actually metal or the sediment off everything”.  They then told me they put the pan back on and put more fluid in the car put that then it wouldn’t go in gear.   However I towed the car back to my shop and pulled the transmission completely out.  I haven’t tore into it yet but what I notice so far it that the output shaft can be moved up and down about half a inch I know the is far from normal.  If anyone can help with letting me know as to might what have happened here and what I might expect to see when I tear into it I would really appreciate it.  Also if someone might could direct me to a website or two of some diagrams and complete breakdowns of this tranny along with a good place to buy replacement parts.