Anything you have to fix in regards to body work, is about labor vs. a replacement part. I've turned down many jobs in the past because I knew I could get a part in a junk yard for $150, but I would have to charge $300 minimum to repair the existing metal. Always remember though no matter how bad it looks it can be fixed if you can't locate a replacement.
The floor in my K5 was so bad it had to be cut completely out including all the braces. The factory panels and braces would have run me around $400 just for the sheet metal parts plus a lot of my time to weld them in. So due to limited funds I started with a flat sheet of 16 guage and 3/16" plate that I had $120 in, and built my own floor design. The result was still very time consuming but better strength, and more options to add options later.
The point is sometimes it's better to just swap parts, but you should still learn whatever you can when you can, and add a few tools to your collection evertime you see a good deal.