Lookin for name of and who carries body panel 72 Dart

I have a 72 Dodge Dart I am looking for the panel that runs between the back window and the trunk. I don't even know what it is called. I am new to the hobby, am I crazy for thinking I can handel the body work? My quarter panels are rough at the bottom, my rockers are rough. I don't want a show car just a nice car, I love to drive hard not show. I can weld and I am a good mechanic. I would love any advice.