As far as aftermarket parts go, a skidplate doesn't seem like a big deal. The dealership should be happy you're there to begin with because oil changes are one of their big winners revenue wise.
I'm getting CBI front and rear plates (one day haha, ordered about 2 weeks ago)... and I'll be going...
Same spec, SR DCSB 4x4, stock wheels and tires, air dam is gone and I added Rokblokz mudflaps (thought they may decrease mpg), no roof rack or bed cover... I'm seeing those numbers too, 20-22 urban driving, easily 25-27 for freeway trips.
When I get more offroad friendly tires I am going to go...