Stuff in the drip rail is seam sealer. Normal for it to be there. Take a trip through my build thread. In the cab work section you will see a lot of that same problem.
On your driver floor, you need to check the cab mount real close because it butts up there and connects right about where your hole is.
The good news is this. Other than your drip rail problems, none of that other stuff will show to the outside so your patches don't have to be beautiful, just functional. If you have the ability to lift the cab off the frame and lay it on it's back, those repairs up under the front get a lot easier. You are going to have to at a minimum pull the bed so that you can work on that rear section.
I hate to say it, but after going through this, it's probably worse than you actually think.
Body shop cost to fix all of this will probably far exceed the value of the vehicle so that is something else to think about.
On your driver floor, you need to check the cab mount real close because it butts up there and connects right about where your hole is.
The good news is this. Other than your drip rail problems, none of that other stuff will show to the outside so your patches don't have to be beautiful, just functional. If you have the ability to lift the cab off the frame and lay it on it's back, those repairs up under the front get a lot easier. You are going to have to at a minimum pull the bed so that you can work on that rear section.
I hate to say it, but after going through this, it's probably worse than you actually think.
Body shop cost to fix all of this will probably far exceed the value of the vehicle so that is something else to think about.