Shouldn't cost more than $250. I would call the dealer and ask what the book time is. I think they only get 5 hours to R&R a trans/transfer in a Silverado SS. The only parts you need besides the gears is a front and rear pinion bearing and a new crush sleeve. Try and go to a driveline shop they will have the best prices and probably the fastest turn around.
Dave
2003 Silverado SS here's where my money went...Radix @ 9psi, Vortec IC tank, Oversized Heat exchanger, ASM LT Headers, Suncoast Ram Air hood, Airaid intake, Trailblazer Torque converter, Full billet servos, Zippy kit, cat-free, Flowmaster muffler, Gaylord Speedstur tonneau, 3/4 drop with Belltech spindles and leafs, Sirius conversion & MTX thunderform sub box. 05 e-fans coming soon!