Remote start...suggestions and install.

I'm considering purchasing a remote start system for my wife's 04 Mazda Tribute for Christmas. I'm looking at the Viper systems since they get some of the better reviews for the systems in my price range. My questions are in regard to two items:

Ease of install
Long term effects during cold starts for short drives.

I can purchase a system at Best Buy and have it installed. Advantage to that is if anything is wrong, I can take it back to them and have them fix it (hopefully at no charge). Problem is, I can save money buying the unit and installing it myself.

Overall, how difficult was it to install (granted, I know most of you have installed them on Tacomas, but the overall install should remain relatively the same across vehicles)?

Secondly, my wife's commute to and from work is only about 8 minutes. It's time enough for the engine to get up to operating temp, but I've heard there can be some concern of static warm-up during cold temps. Any validity to this?