I bought mine off Corwin-Arms, and I can say that when they say "select-grade" - they mean it. Fantastic bore and wood in great shape, a very "smooth for a Mosin" bolt (I'd shot a number of different friends' Mosins before I bought my own, so I was familiar with the range in how smooth the bolt could be).
Buying from a dealer with a really good rep might cost an extra $10 or $15, but worth it for the peace of mind. P&S Guns and Militaria also has a good rep, and so does Weimajack(sp?) in the Equipment Exchange. I specifically bought off Corwin-Arms because I just hadn't heard a bad thing about them.
If you want to save a few $$ then you can find better deals at Canadian Tire and Wholesale Sports, but very definitely inspect what you're buying before you put your money down, as the ones they're selling will vary wildly in quality. And take some latex gloves with you, otherwise your hands will be covered in Cosmo-goo by the time you're done checking them over and picking one you're satisfied with.
You'll be hard pressed to find an unreliable Mosin. It can happen, but by and large they're built like tanks and even by bolt action standards, very simple, so not much to go wrong with them other than a pitted chamber or bore.