Considering 1990 Quattro wagon...?

[Benjamin Weste Pearre <bwpearre@CS.Princeton.EDU>]

I apologise if this is not a good place to ask questions like this.  I
do'nt know where else to ask (my news service went awry some time ago
and hasn't come back online yet).

I have the chance to get a '90 200 quattro wagon.  I know it's a rare
car and all, and it's in good condition.  Seems it's been quite well
maintained, actually, and has not had many mechanical problems.  The
car has over 100000 miles on it, though, and the seller (a private
party) wants well over the Kelley Blue Book dealer-sale value for it.

Ther are a few minor problems, such as LEDs that don't work, and a
couple of switches that work only intermittently.  The car seems to
run well.

My question is: how much can I expect to spend maintaining such a car
as this?  It'd be just wonderful to buy it before ski season gets
really underway, but in the long term how reliable is the car?  What
kinds of things are likely to go wrong?  Will it leave me stranded
somewhere without any means of getting home?  If an Audi has a pretty
good history for breakdowns, is there a time in its life at which
they're likely to start happening markedly more frequently?  Or do the
cars experience a ggentle decline?

I know that these questions are very hard to answer without knowing
much about the car, but I'm just generally asking, I guess, for
blessings or caveats from other owners.  This would be my first Audi.
I don't care that it's a classic, although I'd take very good care of
it: I just want a car that will serve me well functionally.  Pat me on
the back or tell me I'm insane!

Thanks!