I'll start things off:
-What were the engine options in these?
Only the 305 for civillian cars, 350 optional in police package (9C1 option).
-How can I tell what engine is in it?
Check the sticker in the trunk (called a SPID label). Look for the code L03 (305) or L05 (350).
-What would be the engine to have?
Depends what you are looking for. 305s are fine, reliable transportaion. 350s make a bit more power, but will only come in cop cars. As a result, you usually get a car that has had some hard miles, and definitely won't be as plush as many non-9C1 cars.
-How easy is PCM tuning?
There is not a tuneable PCM in the 93 and earlier cars - it is an ECM that has replaceable chips. To tune radical changes, you will have to get a chip burned. To sum up, not easily tuned.
-Any downside to this year as in suspension, steering, transmission, or engine maintanace?
No. The upsides are that engine tune-up parts are cheaper than LT1s and L99s, the tranny will likely last forever (L05s and L03s don't make enough power to really test the 4L60). Good news is that just about every suspension and steering upgrade that goes on an SS bolts right on that old 92, as well
Bottom line: buy it for a good reliable cruiser. If you want a hot rod, look for a 94-96 LT1.