I've used oDesk several times though for other things and it works fairly well. My suggestion is to write up a short "test" project and hire out five or six competent looking VAs. Give them a hard deadline (two hours tops, etc) and see who completes the job in a satisfactory manner.
Some will totally suck, some will never get back to you, and a few will be awesome. If your entire group sucks, ditch them and move on to a new group of candidates.
Once you find someone that is good and in your price range, give them a larger task and see how it goes.
