hey, first off good choice in picking a bimmer, instead of some riced out POS or a big ass truck. I too am 16 and got my 93 325is for my first car.
the e36 tends to have problems with the cooling system, i know mine did. If i were i would take the car to a reputable bmw mechanic (not the dealer) and have him check it out and drive around with you, well worth the money.
as for mods, the chips cant be remapped, because they are OBDI, you need OBDII to remap it with a shark injector, but dont worry, OBDI is better, less restrictive. and there are superchargers and turbo chargers out there, Dinan and Active Autowerks make some of hte most popular models. BMW motors can handle forced induction fine, as long as you do it correctly, granted the engine may not last as long, but these cars last for 300K usually no problem so i dont think you have much to worry abotu there.
hope this helps, once again, welcome
<img src='http://img268.echo.cx/img268/1430/zkwsig23iq.jpg' border='0' alt='user posted image' />
1996 328is Black
Suspension: MB Motoring 18x8, Kuhmo Supra 225/35/18ZR
Audio:Eclipse CD3414 HU
Lighting: ZKW W/ DDE PLUS