Get on overclock.net, BW. You won't find a better place to learn overclocking all at one forum. Well, you have extremesystems.com but they have slower servers.
As for the upgrade, get rid of that GTX260 and slap whatever upgrade you can afford in there instead. Your proc is probably bored.
Do NOT overclock that cpu more than max 200mHz with a stock cooler. They emit heat faster than you can say barbeque.