remote start in 03 Avalanche

I would like to get a remote start possibly a security combo.  I have heard good things about DEI products and was looking at a Clifford, Viper, or Valet systems.  I would also like a 2-way system.  Range is important since I have to park quite a distance away.  I found the Valet 554R system on ebay for a very good price. I contacted some installers for price to install but they are too pricey for me.  I am not sure if I can do this myself.  I am very mechanically inclined, but lack a bit when it comes to electronics.  I can wire stuff just fine if I know what goes where.  I also am afraid that I might mess things up becuase of the factory security system.  How hard is such a job?  Any tips/pointers/advice?  I found the wiring diagram for the vehicle online but I am unsure how to read it properly.  It would also be great if I could turn on the rear defrost and possible the heated seats.  I am I pushing my luck?

With the 03 Avalanche, becareful, alot of multi-plex wiring in the vehicle, best bet is get a GMDAA(Gm data interface module) ask your local install shops for one, this module SHOULD, key word should control your defrost lines in the back, this unit will do your passlock and doorlock interface, and follow the instructions for alarm doorpin wiring hook-up, because this unit will do it as well.  Overall those vehicles aren't that bad to do, just don't test anything you don't have to!Kyle@Audio Obsession Sound

yeah messing with the passlock 2 and the class 2 databus  thing with the doorlocks is more work than its worth if you dont buy those modules.  othewise u have to 5 wire each lock and unlock wire on all the doors.  which is way more work than necessary.