Welcome, this is a great resource for a project like yours. You can look at my pictures and progress on a similar project that I have been working on for almost a year.
Before you pull the cab off the frame you need to brace the door openings. Your door hinge post looks pretty solid but verify the door fit and if okay then brace the opening to keep everything in place when you remove the cab mounts to the frame.
I had my frame blasted and painted at a local shop.
