I'd say go for the wireless mighty mouse. I've had mine since I bought my iMac early 2008, and never had a problem with it. The mouse is used for at least 6 hours every day. No problem with the scroll wheel, but I do clean my system every week.
Instead of the Mighty Mouse, I'd recommend checking out what Logitech has to offer first. Congrats on the purchase. I was a kid with computers for toys since I was 12. Finally started using Macs when I went to Uni. I can't imagine using PCs if I wasn't paid for it.