I'd rather cut away sheetmetal than deal with the rear subframe.

5W-30 is too thin. the oil won't stay in the cam/valve region long enough. I'm running 10w-60 synthetic and it helps the engine stay calm and quiet. It's also excellent for track day use.
I tried 0W-40 synth, 5W-40 semi synth and 10w-40 dino in various p80ies, and 10W-60 is by far the best.

shout-out @xanthefin
He might be able to help

There are 2 versuons of that 3rd brake light module. One is for the bulb version, one for LED. If they are incirrectly used, it can cause the light to go on.

if it's the rear and that feels shimmy, it could always be the delta links or the other horrible bushings whose name thou shalt not even say or write.

no part left behind!

since it's a 99, you don't have the boost gauge. Honestly, if you plan to drive it for a long time, get it fixed. I wouldn't want to waste boost nor risk blowing the motor. The first BMW Turbos in the 70ies had no wastegate, and beside the danger of that because it wouldn't release pressure before e...

These are the Bearings I used for my 96 R that Inswapped from AT to manual (using a M56 out of a 96 Turbo). They should fit a 20V NA as well.

I bought a 93 Civic VTec with a broken timing belt (it broke while it eas idling) anf after slapping a new belt on it drove just fine. vtecs are intereference, as well, btw.
you and your daughter might be lucky, but as others said, it's not very likely. I'd give it a go after using an endoscope camera

not a convertible, yet. just add sawzall.