First get your wife to buy a new keyboard ;-)
Then, if this is your first tear down, get yourself a set of tools. See the guide for reference. I got mine from ifixit. I have used the guide Ben refers to. Very accurate and useful. Make sure you don't mix the screws up! I used a fair sized piece of paper towel laid down on the table top and scribbled onto it the steps # for each set of screws and size (some steps have you remove several screws of different size). Don't fear, though, the guide is thorough in its steps. Make sure you read them all before starting, it helps. Also have some heat sink paste (instructions and links in that guide).
My friend got a used keyboard for 39$ but I don't have a reference. I'll try to get it for you.