cygnusx-1

Just recently put a reman BAYA in my TL, and it seems to be holding (2k miles since install). Haven't really had any problems with her yet, so I'm considering throwing some money at it.
Any decent mods for these cars still around? I'm hesitant to do any performance mods due to these transmissions being glass, and don't want to test my luck again. Maybe an exhaust as someone mistook my muffler for a cat and attempted an impromptu removal.
Needs a new head unit and probably an amp/speaker install, and interior is wrecked from the previous owner. I was wondering if anyone had any experience installing a system in these cars, or redoing portions of the interior (Headliner, dash, seats, etc). I've done 3 installs before, but they always have their challenges.
I was also considering coilovers, rims, and a brake kit. Maybe a minor ride height change (1.5 inches). Anyone have any good recs?

Thanks for your time. Just trying to keep an old car pleasant. Spent too much time under it to not enjoy driving it.