Just saw this in the ad from the sunday paper. You have to pay $5 for the preorder, and you get $15 of MUT content probably when you pick up the game. It doesnt list any restrictions, just says not available in all stores. It does state video game must be in original packaging and customer must be 18 years of age or older.
Ive noticed their trade in values seem to be based off best buy, as they are usually a few cents more or less. This is in store only i assume.
to check values or find out if your store is participating (blue find your walmart square next to search)
link to ad (on page 23, middle left of 2 page layout)