1. Typically, most LS roller cams require 7.400 pushrods...unless the cam is ground on a smaller base circle and head work has been done.
2. You can squeak out more lift by using a higher ratio roller rockers. I wouldn't go any bigger than 1.75 or you will have to modify your valve covers.
3. Depending on mileage and condition of gaskets, you should be able to get away without replacing any of them. BUT since the Water Pump gaskets are cheap, I would replace them. Also (depending on mileage), check for extra slack in the timing chain.
4. Best way---search cam swap and read some threads about it. If not, use LS1Howto.com and read the instructions. There are a few differences between the F-body and trucks, but you'll eventually get it.