Trunk pan replacement

I have a 1979 Z/28 Camaro that needs the trunk pan replaced.  I have never replaced a trunk pan before so I am looking for any advice to make this job go easy.  Can you guys give me some tips on cutting, fitment, installation, etc.  I plan on installing the new pan with a MIG welder.  Also, I am looking at pans from Goodmark, Year One, and Paddock Parts.  Which one of these vendors provides the best quality sheet metal? Is there a better vendor than these three?  I am trying to keep the install looking original.

I replaced the trunk floor pans in my 68 Lemans. I didnt do the welding, though..know my limitations- had a body shop do that, so cant help you there. I got my parts from tamraz on ebay, Goodmark 3 pc set, body shop said the 3pc tended to fit/work better than the 1 pc set. Very solid parts, would definately buy them again. After the factory splatter paint, the trunk looks almost brand new.