Roof vent repair

How old is the camper? It may be due for caulking maintenance of the roof penetrations. That should be checked/performed every season.

I walked on the Roof of our 2003 Bigfoot with no issue. I was only 200ish back then though.

It would be much safer to do it from a ladder. When I service mine I'm always on the ladder.

I don't know if they come with the screw holes already drilled, but if they aren't you could match them up by measuring each one. Kinda tedious, but at least you won't be drilling additional holes in the camper body that way.

Always place some caulking around each screw head and screw threads if you use caulking.

Another way is to use the butyl tape like the factory and screw down evenly while is squishes out. PLastic scraper will get the excess off without scratching. If you ever have to replace it again you won't have to go crazy getting it off.

Stove vent? Usually these vent out the side. Refrigerator vent perhaps? At 240, I made the mistake of stepping on the hump on my old 'foot, causing a superficial crack in the glass. I'm careful to step over the hump now along with avoiding all the other obstacles.

With an adequate ladder most repairs and maintenance can be completed without walking on the roof. Much safer for you and the RV IMO.

When you buy the vent cover, be sure to also buy a tube of Dicor Lap Seal.

Yeah, I agree with @donn0128 about gluing the broken cover back together. I had to replace mine in October, and I think it cost about $5. Camping World sells them, but you'll have to ask at the parts desk. Not sure they are shown on the web sight.

As for the roof, I, have no insight, but I stay off mine (I weigh almost as much as you).

Plasric vent covers are cheap and easy to replace. At your weight I would not venture up on the roof without additional support, like a sheet of plywood.