i have an 85 cherokee with the 2.5l with 4sp. I can not get it to shift into reverse, what could cause this? would it be cheaper to rebuild it or get a new one? Weres the best place to find a new one or parts?

so if thats the case, is it something i can do in my garage (ive done engine swaps and most things on my own)? do you need any special tools? wheres the best place to get these parts?

All you need is a little patience, a clean work bench and a pair on snap ring pliers.
Parts kits are still available from Napa I think.

how can i find out what tranny is in it? will it say on it?

In my opinion, anyone who needs help on how to identify their transmission probably should not try rebuilding same said tranny, having said that, there were only 2 options for the 4 banger manuals, the ax4 and ax5, both of which are weak transmissions.