You'll know if your computer has USB if you can plug one of these into it somewhere.
I don't really know much about MP3 players... 256MB is decent; it'll hold about 50 songs, depending on the quality. Never heard of Visual Land before, either, and I usually don't trust brandnames that I've never heard of before. That doesn't mean it isn't good, though.
I recommend going to an actual store to buy one rather than getting something off eBay.