Need Help deciding on Rims/Tires w/ TONS of Questions

OK, I got my bonus, so I want to put some nice Chome RIms and new Tires on my truck. (As well as finish the other things on it from my Wish List). But I am mightily confused. I have never added RIMS to a car before. My last car was a Mercedes SLK230, and it looked fine IMO, so never was interested (not to mention, doing ANYTHING to a BENZ is always 4 figures or more seems like - MINIMUM).

I REALLY like the 20" Rims some of you have done, but cutting up my mud flaps doesn't appeal to me. If I put the Stillen 2" lift on the front will they fit w/o having to do that? But what about ride on tires that thin? Seems like tires that thin would totally get f*'ed up on the slightest potholes or curbs, etc? Input on this matter much appreciated. I saw some 20" American Racing chromes with Pirelli Scorpion ST's that looks just awesome, but is that realistic for a daily driver?

Also, I am wondering if I totally lose my 'truckness' of the truck with tires that thin. Would 18" better and still let me put decent truck tires on it? I do NOT go offroad, just onto some Forest Service Roads at worst, mainy my truck is an Urban go-getter/commuter.

Really interested in some options. Tirerack doesn't list our truck for fitting. I think I will swing by the local 4 Wheel Parts store or Discount Tire and see as well, but looking for some input. Thanks!

Bin

Oh yeah, one more thing - can the speedomoter and odometer be adjusted to take into account new size tires? Does the shop do this?