Ok so I made a smidge of progress this morning. I cut the hole in the lid, my poor little dremel was not happy about it
Getting ready
Oops I broke the cutting disc, luckily I have 20 more
First layer cut, hey wait- didn't someone tell me these were hollow? Darn it
Don't tell my hubby but I may have sacrificed a steak knife to cut the foam, and then I used the steak knife to mark the corners on the next layer, I also used a little sauce pan like a hammer

the knife did not survive, but may be gluable
Oops I broke another one, Mann do those little pieces fly! Where are my safety glasses?
Alright I'm through but didn't do a good job marking the 2nd cut
Hmmmm need to figure out how to take that edge off, already put the dremel away.....
Ummm no pictures of this lol, but I tried a block plane, then saw a saw, I went with the saw. Rather over sized for the application but I propped the cooler lid on a gallon of paint and went to town, I held the lid in place with my bare feet (I do have a brain, it just wasn't in use at the moment), my feet survived and I got that edge taken care of. I used a flat exacto knife (like a chisel) and took the jagged edges off too
Good enough
My hubby told me where the drill is but told me to mark where I wanted it drilled and he would do it when he got home from work. Probably a good thing he wasn't home to see my escapades this morning