If you have never used power tools then you might want to go to local hardware store and check out their weekend clinics, Home Depot, Lowe's, Menard's all have them.
Check out Diynet here:
http://www.diynet.com/diy/diy_kits Check out article in shelving, wood working, etc.
You must be pretty good with geometry since you will need to get precise dimensions of the entertainment center as well as angels if you plan on adding molding around the top.
It's not exactly rocket science but it can still be challenging. Good luck!