If you plan to change at the prescribed intervals, then the question of synthetic versus non-synthetic is relatively moot. The non-synthetic will start to "go bad" a little quicker, but should be relatively okay by the oil change. I prefer synthetic, but only when I can afford it.

For our weather, 5w is okay. 0w is kind of risky if you're not sure about the engine's condition, as it might be too think. I usually run 5w - 10w on my cars. Anything higher will cause increased consumption and drag on your engine... trust me 5w feels a lot "lighter" than 15w.