Spell it out for me-I'm slow

Can somebody give me a breakdown of the various connectors and boxes I will need to install the following:  an aftermarket head unit but with full utilization of OnStar will all the chimes, etc...and four 6.5" door speakers and new tweeters.  I would appreciate it if anybody can point me to a retailer you trust who offers all of it-the OnStar interface, radio wiring harnesses, and door speaker harnesses.  I don't want to cut and splice a THING.

Thanks!

Bose ? Monsoon ? or base factory audio?

Guess that would make a difference, huh???  Ooops.
 
My 3 has the base radio, no bose, no sat, no nothing.  I would appreciate it if you guys could suggest a place to order from that you like, too.  Good service is just as important to me as is the price.
 
Thanks again!
 
 

I went with the Valor DTS-660W a Pac OS-2 and chime module however I have disco'd the chime it drives me crazy.
I am a retailer so if your interested let me know

I sent you a message.  Thanks!