Look at my "Rebuild of Creeping Death" build thread. Link is in my signature line. The metal cutting started on page #7. I have never done body work or sheet metal work of any kind. But I can weld and have a nice welding rig. So I tackled all the cab rust/rot out of my 1972 GMC. I detailed all the trials and tribulations in my build thread.
One thing I will tell you... the rust you see is only a fraction of the rust you have. So be prepared to replace the entire inner rockers (cab floor extensions), outer rockers, part of the floor, cab corners, front and rear lower pillars, front and rear cab supports, and kick panels. It was a lot of work and I learned a lot. It took me quite a while, but my rig isn't my daily and my work schedule sucks. If you get stuck, stop and ask. I have a couple local cats on speed dial on my phone that really helped me out to explain things as I went along.
Gary