I use this.
http://www.opti-lube.com/dfi.htm
I used to use their other product here when I lived in colder climates:
http://www.opti-lube.com/XPD.htm
But after talking to their customer service person, since it doesn't get cold where I live now compared to Colorado, and I don't need to add Cetane for extra performance mods, I can get away with the cheaper stuff.
I add it every tank. They give you a little bottle for in the truck, it treats up to 1500 gallons in summer ratios, so the gallon should last me a while.
Since you are looking at 02, another thing to check is the cabin air filter under the dash, I believe they only existed on 01-02, but if it hasn't been changed, it could be clogged and kill the HVAC motor, which sucks.
I really like the hood/grill on 01-02 GM trucks. Reminds me of the 69 Chevy hood for some reason, but it's probably just my imagination.
Its good to hear that you are going to leave it stock. I seldom hear that sentiment around here and in all honesty, my truck is meant to tow my jeep and haul equipment, nothing more. Money spent on tuners and other crap don't pay for themselves in mileage, let's not kid ourselves. And that is money you can sink into your wheeler. Plus, I really like the look of the stock trucks.
You get the truck? Post up pics when you do.
Cheers,