My LHS sells some motors that are compatable witht the Novak ESC, 19 turns I think.
3000 MAH NIMH Packs will give you a longer run time.
In theory the batteries wouldn't make it go faster. In reality though, it would be like running with a fresh charge until they die, and then it just stops completely. NIMH packs run solid until they die, whereas NICD loses strength as it runs out of juice.