We had a 95 A4 that a customer had at our shop we were doing work on. It had 108k miles, everything worked fine. They only wanted $3500 for it. And it was driven by a girl. Ive seen quite a few on the internet as well floating around. Hell ive seen 98/99 LS1 fbodys for for 9k. But I seriously wouldnt offer that guy no more than $3500 tops. Its not worth much more.

To fix the a/c you are talking a few hundred dollars to replace the line, change the filter dryer, change the orfice tube, flush the sysetm and refill with r134a.

A cd player is another $100

the header gasket, well you can do it yourself, if its the drivers side, then you are lucky and they would take an hour or two to fix yourself. The gasket itself isnt that much.