See my longish post in 'Installation Notes' under 'Becker CDR-220 / Porsche Boxster'. I got mine installed by Monney in Redwood City, $60, 30 minutes, was very happy with efficiency, quality, and access to back to see it installed.

It's actually a pretty easy install (empeg have made things very logical), so my belief is that most places would be able to do a reasonable job.