The trunk floor pan in my camaro is okay,the floor pan extension and side panel that is a step up from the bottom of the floor pan is in need of replacing. I thought this was one piece but it is actually two,and I'm not a body man.My question is how does this or these attach to the lower trunk floor,how do I remove them,and how do they reattach,I assume the are welded in place.Just to clarify, these are the pieces that are on the side and kill of behind the inner fender well and rear 1/4

If you look at the pictures in my gallery, you may be able to see how the extensions and drop-offs are installed and attached.
http://chuckbro.smugmug.com/gallery/858139/5/50746283

The original pan included what is known as the replacement 'extension'. Depending upon the extent of the damage, you can use the replacement panels to cut patches from rather than replacing everything. The extension is welded to the frame rail, inner wheel house and inner tail panel. You need to remove the bumper brackets if there is rot beneath them.

The drop-off is hard to get to with the 1/4 on but you should be able to cut the welds along the wheelhouse and bottom of the 1/4 panel. Getting to the welds along the tail panel may be tougher.

I would look it over and start by cutting out the rotten areas to see how bad the damage is. If it's not too bad, think about patching using patches from the replcement panels.