Piece of cake! Remove the caulk (super plumber's putty?) from the rivets. On a warm day it comes off pretty easy if you take it slow and help by tugging on and end. The faster you go the harder it resists, so go slow and avoid scratching your skin. Then center punch the top of the rivet to drill it out (1/8" drill). I've found that you really want to offset the punch towards you and then drill towards the center--you usually can't drilll straight down, anyway, unless you remove the cover before you start. I also use a "jobber" drill length (18-24 inches, available at Home Depot, etc.) that allows me to have the drill motor above the cover.
Drill out the rivets on the
inside skin (you've already removed the light fixture, of course). Then (and only then) go outside and pry the vent loose, careful to avoid dents, if possible. If you do create a dent, you can hammer it out (I'm using a metal hammer here for a very small, but sharp edge--I usually use a plastic hammer to avoid hammer marks in the skin) by holding a small but heavy/hard block under the skin.
Mark a 14" rectangle. I used the nearest skin edge to establish a true square orientation of the hole. The original installation (on all my 3 Airstreams, 4 years apart) was done crudely, at least the cutting of the outside skin. Shame!
Be careful when you cut the skin away--the wires underneath can creep up to the edge, just wanting to be severed, and you'll never see it from on top. I use left and right cutting aviation snips, not straight. Both of these will cut straight, but have the advantage of being able to rotate slightly and still cut along the line. This rotation will save your hands from the rough edge.
Do not close the snips all the way as you cut--this creates a small crack in the metal right at the tips. Cut close to the corner, about 1/4", then break off the tab of metal (yes, you'll have 45 degree piece across the corner).
You'll also have to transfer that 14" square to the inside skin and cut it away. This Sovereign had all the 12 VDC wires on one side and the 115 VAC on the other. BTW, not true in my Overlander.
File the edges to remove any burrs or inadvertent cracks. The file the corners--this removes what would otherwise be a "stress riser" at the corner.
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