I'm thinking of doing something like this:

So I'll have a duct route the air from my heatgun to the gpu, and I'll go buy a IR thermometer.
What I'm wondering is what I should do for the bottom of the board, should it be heated? IE: Buy an electric griddle.
Do you guys know of any detailed tutorials explaining how to reball the GPU? I know how to remove and clean the GPU, but dont know what solder to use and how to reapply the solder.