Fitting a Becker Cascade Pro into a 996.1 - plug and play?

[Dammit]

I've got the six speaker setup in the car (which is, as far as I can work out, how it came from Porsche):
- CR-21 Becker cassette radio head-unit
- Nokia 6x40w amp
- Becker CDC-3 CD multi-changer

I'm hoping that it'll be a case of pull the CR-21 out, unplug, then plug in the Cascade Pro along with the GPS antenna and the mic, then stuff it back in the dash.

However - when is it ever that easy?

Has anyone done this and can comment?