What's your budget? Are you only looking to replace MB, CPU, and GPU or are you building an entirely new tower? When I was building my PC I found PCPartPicker.com to be a great tool to check prices and compatibility on all the components I was thinking of getting.
My sister introduced me to this browser-based text RPG called Torn in 2006 and I have been playing almost daily ever since. It's not really a big commitment as each session only lasts a couple minutes 1-3 times a day.