These are some candidates i'd recommend. I dont know your budget but i wouldnt go any lower (wattage) - of course you can always get a model with more output.
http://www.newegg.com/Product/Produc...82E16817103936
http://www.newegg.com/Product/Produc...82E16817103927
http://www.newegg.com/Product/Produc...82E16817103459
These have the advantage of 2x 12V rails - so one can power your CPU (Nr.1 major power consumer on the +12V rail) and the other your video card (Nr.2). This gives you exceptional stability.
PSUs are very easy to install. You unplug all connections, unscrew the old one - take it out, put the new one in and plug everything back in.