You want it to shift a 7 speed rear cluster? You can try Sheldon Brown's alternate cable routing trick, which should make the 8 speed shifter index with the 7 speed cassette. I have not tried it personally, but Sheldon generally knows what he is talking about.
Also, would I need a new freehub body if I wanted to put an 8speed cassette on in place of the 7speed so that I could just match the shifters? I read up on sheldon brown's site but I didn't know if that would for specific instances or all of them?
You would need a new freehub body to install an eight speed cassette. Also, seven speed cassette cog spacing is close enough to eight speed spacing that many people combine 7 & 8 speed parts without problems. You may want to give it a whirl to see what you think.