keep in mind 89's where the transition year.. but it is Turbo 5spd those combo supras are really wanted. my suggestion is to do a car fax report, find out everything about it. and find a supramechanic around there locally and go from there.
if it was me. i have another DD. and trading a 91 integra for a turbo 5spd i would do it.
If u could possibly post pics and/or the issues it has? that will help alot, alot of people here can tell u if it will be a costly fix or a maybe just a simple fix.
Another thing to add. Supra's will require some work, no matter what. if u treat it nice ur car will treat ur wallet nice... in most cases... If u end up getting it. CHANGE every Filter, New fluids all around, New Thermastat, Plugs, inspect all ur coolant lines, any foul play such as half assing, redo it the right way.