1st time Cadi owner :)

I just read through the 1st 25 pages of posts here to get an idea of what issues/problems I might look out for on the 92 Deville I just got off lein sale for a steal (way under KBB price for condition it is in)

Thus far I found no real common probs that are addressed here which is a good thing, right? :)

That said, some of the few probs I have on the car (and hopefully will get replies back in fixes)..

[1] The readout that shows MPG says either 0 or 70 (Shaaa, I wished). is this a replacement of that system's control module or ... ?
[2] Radio has power, but I get nothing when trying to listen to tunes... new radio needed and if so, any issues I need to be aware of if swapping to an aftermarket double DIN am/fm/cd player?
[3] A/C needs to be charged, blows outside temp aiur... is this a pre or post conversion engine?
[4] Tires all "appear" in good shape but I get a shimmy when driving (start through all speed ranges)... tie rods/ball joints/ other suspension probs likely?

thus far that's all I have found wrong with the car other than 1 minor cosmetic issue (driver fender top turn signal seems to have had cover ripped off taking part of the fender with it (thinking bondo and a new cover to fix :) )

ty for your time and any replies in advance