I'm just now starting the body restore on my '92, as the upstate NY winters have taken their toll. I thought I'd share this project with you guys as this is a very common problem with broncos and comes up time to time in these forums.
This can be a tricky task for a first timer. Someone who has never done this before could very well spend as much doing it himself as a shop would charge because of the specialty tools you may have to buy. If you have access to a mig welder and a compressor you can probably do it yourself and save quite a bit of money.
I didn't buy full quarter panels for my truck, just the wheel arches and spliced them in. I bought the arches locally for $55 per side, but you can find them for much less on the internet.
I first used a body grinder to cut out all paint and previous body work ans assess the damage on the quarter.
I then cut out the entire rusted section of the quarter panel with an air powered cut off wheel. It is important to take careful measurements before cutting anything so you get the patch panel on correctly.
I then straightened the tiny imperfections of the cut edge using a body hammer and a dolly block. It is important to do this carefully and only straighten but not stretch the metal.
Next I used an offsetting tool to create an offset on the quarter panel cut edge which is the same thickness as the patch panel for the patch panel to fit into.
I then carefully cut the wheel arch to fit inside the offset on the quarter panel, sprayed the mating surfaces with a zinc coating to prevent rust in the future, and welded the panel in place.