www.cadillacfaq.com on most of your questions:
the others:
UUC can be purchased from Lindsay cadillac I believe (they are a supporting vendor/ dealership too!)
Navigation works off the DVD... no membership is required
See the FAQ
Mods: Its up to your dealer... some will allow a Maggie SC without any issues... it really depends.
See the FAQ
Buy the package that includes clay bar, Z1, Z2 and Z7... Start from scratch your first time (it will take a day or so to do, but its worth it)... Its not difficult to understand, its actually quite easy, its just time consuming to apply (but you are doing multiple coats)
www.zainobros.com
Sign up on the registry (
http://www.cadillacfaq.com/faq/reg/
Welcome!
Reed