I recently replaced both vents with Fan Tastic vents with 3-speed fans.
I was told not to walk on the aluminum roof without putting down some planks to spread my weight. There's not as much material under the aluminum as there is under a ribber roof.
This is what I'm using to seal the edges. Its made for aluminum roofs.
Kenny
1996 Jayco 376FB Eagle Series TT
1997 Jayco 246FB Eagle Series TT
1976 Ford F-250 4wd Mercury Marauder 410 - 4V
Regular cabs. The best looking trucks.