Retrofitting e30 with e36 Business CD

[Thud]

I've posted this on a few forums already; I was able to find an OEM Business CD RDS (CD23; Blaupunkt Model BP3850) from a 1994 e36 very cheap (try the German eBay site). I intend to install it in my e30 to replace my barely working OEM-ish* head unit (cassette), and I'm looking for some info from anyone who has done this before (I know a lot of people have). I do not have an owner's manual.

* I say "OEM-ish" because the unit is actually older than my car by a few years and has some archaic connections compared to newer units. Whoever installed (or re-installed) it did a lot of creative splicing.

1) I already have the wiring harness for the new unit (BHO8590), so that's not an issue, and I'm pretty sure I can figure out the connections for that with relative ease. However, someone did a hack job on the wiring in the car's previous life (probably put in an after-market and then replaced it before selling), so if anyone has a color-to-color matching chart, that might be helpful.

My current head unit has a double brown ground wire that screws into the back of the unit; not sure how to adapt them to the new unit. Any ideas?

2) The connector on the antenna cable I currently have in the e30 (which I can only assume is OEM, but can't be sure) does not fit the antenna plug in the back of the new unit (the cable's connector is too big); does anyone know where/if I can find an appropriate connector/adapter? Or do you think I need to buy a whole new antenna cable and do a cut & splice?

3) There's a small port on the right side of the back of the unit (next to the wiring harness connection) that looks vaguely like a miniature BNC-type connection. My assumption is that it's an auxiliary connection for a special antenna or something, and not anything I need to be concerned with. If anyone knows otherwise, let me know.

Anyway, if anyone has any info regarding this installation I'd welcome it. Thanks.