Here's all the stuff you need, as well as some useful links.
OK, lets start with the MOSFET chip. The original chip that was installed is no longer produced AND was replaced with a new (better) version. Kinda makes you wonder if that's why the original chip died to begin with...
The original part number is:
SUB75N06-08 which is made by Vishay. Per their website, they replaced that chip with:
SUM90N06-4M4P (this is the one you want)
Here is a link to the chip on the site you can get it from (for a whopping $3.59)
Here is some MOSFET Soldering and info:
Aside from the actual chip (which is the only part that you need to replace), you will need:
Arctic Alumina Thermal Adhesive (NOT Paste)
Solder (1mm Lead-based solder is probably best)
High-Wattage Soldering Iron
Solder Wick (to remove old solder)
4 M4 x 25mm Screws (preferable stainless)
1 small piece of ABS plastic or other sheet of plastic
Rubbing alcohol and Q-tips
All in all, depending on what you already have, the cost to do this project is about $15-20 in materials. I will assume that most people have a soldering iron and dremel.