ORIGINAL: skeeter 7MM
Try looking on some optic sites like Opticzone, etc or ebay to find a Bushnell Elite 4200 3x9x40, selling below 300 I don't think there is a better scope for this price right now.
My thoughts exactly! At $300 or below, nothing comes remotely close to this scope. Even up to $400, it holds its own against some very fine competition.
http://www.budsgunshop.com/catalog/product_info.php/manufacturers_id/145/products_id/21475
http://theopticzone.com/detail.aspx?ID=4094
http://www.swfa.com/pc-7280-185-bushnell-3-9x40-elite-4200-rifle-scope.aspx
http://www.bearbasin.com/catalog.htm#b_l_scopes
As for mounts, I'd suggest Talleys or Leupold Dual Dovetails.
If this is your 1st real scope, does that mean the .300 WSM will be your 1st real rifle? Make sure you get plenty comfortable with it prior to heading out West!
Good Luck,
FC