Yep, the cab leading roof edge looks to be your most serious problem. Are you a skilled or semi-skilled welder and/or metal man? If not, it might be worth it to at least get a shop estimate as to cost. In the long run it may save you money and certainly time. The mistake that cost me both on my first project was removing too much bad metal at one time. That will really throw the cab into all kinds of distortion unless it is properly braced inside.
So, think it through and take your time. And search through the body forum on this site for helpful advice.
