Best bet is to find a reliable car audio and alarm dealer that is reputable and local and have them do it. The money you save buying remote car starter from Crutchfield or online, etc. will most certainly be made up in labor when you bring it to the installer to have it done. They make their money off of the items they sell, not so much the labor. If you want a good reliable brand, Astrostart makes one of the best ones I've ever seen.
Also try these two sites.
http://www.commandoalarms.com/itmidx10.h...
http://www.northerntool.com/webapp/wcs/s...