I used to hook up my own stereos (head units) way back in simpler times,
but had trouble with my '86 CGT, and now want to work on my '97 A4 2.8
with the Delta CC stereo.  The display has a bad patch, and there's no
CD changer in the car, so I wanted to replace it with a stereo with CD
that had been installed in my '98 A6 QW (which also had/has the Delta CC).

When I pull the Delta CC head unit out, what are the 'gotchas' for using
a 3rd-party unit?  I believe I saw something about a setting (VAG-COM?)
to tell the car that there are no pre-amps on either front or rear...is
that going to be needed?

It's an Alpine deck, older model (approx. 2 years) with CD and XM
capability, but I don't have the model # handy.

I was HOPING that because this same deck had been installed in a similar
situation (replacing the A6's Delta CC factory stereo) that it would be
reasonably easy to do the same in the A4...

I wasn't able to find anything quite right with Google, but pointers to
other sites with info like this would be appreciated, or a quick
sketching of what's required here would (of course) be great as well.
Thanks...

Bart