Purchase help 1999 2.3 auto

I have identified a 1999 Z3 2.3 auto trans as a potential addition to the garage. Here's the details: 29,000 miles, garage kept, seasonally driven, one owner, drives great, traded in on a new luxury sedan by the owner. Now in the hands of a high end luxury dealership.

Asking price under 14K. On a whim, (I own a 03 z4) I test drove it and it had the "loose" seat issue on both seats. The dealer called the BMW dealer and was told; $2000 to fix. I know I can have it fixed for about $500. Now they are down to under $12000 for the car. I offered $9000 and I would give them a liability waiver on the seats. I don't believe they will sell to the public because of the seat issue, so I believe they will go lower, but I'd like a little ammo from you guys.

It has new tires put on by the dealer before the seat issue came up.

If you had a 1999 Z3 that drives great, dropped in your lap without any service records, what preventive maintenance would you do immediately to properly freshen a beautiful Z that just hasn't been used much? Also if you could ball park what the dealer might charge. I will then use this when I recontact the dealership. BTW, the finish on the car, top, wheels, interior is 9+.

Auto trans service,?
radiator flush,?
differential fluid change, ?

What else????

Thanks guys.