don't bother much with mods for performance. they aren't really worth it. it will still be a somewhat slow car. if you want something, just go with a cat back exhaust. have a chat to your local exhaust shop to see what sort of money it would cost. should only be a few hundred for them to make something up for you from mild steel.
as for reliability, they aren't much different to any other 20 year old car. just regular servicing, etc.