Nothing was wrong with my macbook, but I wanted to make the keyboard backlit. I bought this makbook in late 2008, right before they refreshed the 13" model, making it a 'pro' and adding a backlit keyboard as a standard feature. Luckily, iFixit has a guide for this, and so I went about purchasing the top case. The only one iFixit offers is a used one for $300+, and I didn't want to spend that much. I found one from a company called DVWarehouse, new, for only $189. This one didn't come with a trackpad, but I didn't need one, I would just use my old one.
It went pretty well, with a few rough spots, particularly with the right speaker removal (any electronics repair where you have to remove something that is adhered to a surface is always difficult), motherboard replacement, and trackpad replacement.
I left a few notes on the guide, but one thing stands out. If you are buying a topcase from a source other than iFixit, and you have to take the trackpad out of your old case and put it into the new one, this will most likely be the most difficult step you will go through. Have patience, and follow iFixit's directions to the tee. When screwing in those tiny YO screws, BE VERY CAREFUL TO STOP TIGHTENING THEM AS SOON AS YOU MEET RESISTANCE. These screws are VERY weak, and I broke the tops off of two of them when trying to re-install my trackpad. Fortunately I was able to remove one of them, but the other is now permanently stuck in my trackpad, as you can see in my second photo.