look at the vid card's manufacturer's website and check the minimum requirements... i highly doubt the 420watt will have enough power... but wattage isn't the only thing to look at, also look at the amperage on the 12V rail..you'll need 26.. yours probbaly has less than 20.
ok I will upgrade that but how hard is it to change the psu? on a scale of 1-10 1 easy 10 hard what would you say thanks I just wanna know if i could do it or if I should have someone else do it for me
A PSU isn't hard to install, maybe a 2 or 3 if your a beginner. You could do it yourself, but if you want to feel safe you could have someone else do it. Just don't pay anyone to do it, because it is pretty simple.