The Pawn Stars Shop is kind of a bust, more of just a tourist trap place. Half of the floor space is filled with junk merchandise. Unless you really love the show I would not go out of your way to see it.
The Wynn does have a nice auto collection but it is very small. You might be more interested in Auto Collections at the IP - http://autocollections.com/
When I was in Vegas a couple weeks ago they have discount tickets at the 1/2 Tix booths.