I think walnut is a fine wood to use... the only issue with using one piece like that, is being certain you won't get 'cupping'... which is difficult without letting the wood sit for some years. If you laminate, it's more likely to stay flat. However, that said, at $35, if it's a beautiful piece, and it's for you, (and a bolt on neck) I'd go for it and just see what happens. You can do some research on the internet and find the most likey way woods move in relation to how they were cut from the tree. I've seen some georgous walnut 'crotch' wood! I intend to use some, at least for the front and back, pretty soon. I've got a 3" thick by 8" wide piece of walnut that's been sitting for 6 or 7 years now
Brian