Rust help Please..fixable or not?

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I just picked up a 70 3/4 ton. The cab floor looks good for being in VA. NO rust in the cab corners and the rockers are original and just started to rust. (Texas truck) but there's rust in the channel above the doors of the cab. It is where the channel curves to wrap around to the side of the cab from the windshield. It's in the curve on both sides the rest of the channel looks good but it is the entire curve. I haven’t started to pick at it yet to see how bad it is. It doesn't look good because if you open the door and look at the underneath side it has rust that I haven't messed with yet. Someone in the past filled the channel with silicone thus I can't see how bad it is.
There is also one pin hole of rust that is hardly noticeable inside the cab above the windshield. Is this fixable. The rest of the cab really is in good condition. I would hate to loose it. What would you do? IF I look for another cab it would be hard to find one with a great floor and cab corners. Should I use a wire brush on a drill and fill it with bondo? How could I prevent the pin hole from getting worse (above the windshield?