I removed and replaced three window units on my
Burro. It was elementary. The
windows were held in place by an inside clamp ring that screwed into the frame all around. That exterior frame was bedded in caulk to seal out
leaks. When I installed my new
windows I used butyl tape caulk. Carefully clean off all dried old residue caulk. Most of us will advise against using silicone caulk of any kind, as that stuff always fails.
Best advice is take good care in handling that inside clamp ring. Having to buy a replacement will likely choke your bank account, big time.