First off the headlight covers are just a plastic piece. The windows are dual pane window glass with gas between them and sealed. So the only good way to fix it is to remove the seal and clean it inside and seal it. When we took ours off I removed the screws on the inside and went outside to pull out the unit. My wife and I handled it easily. It is not heavy, just bulky. Leave the frame stuck to the inside and not remove it. That will help you realign the window when you put it back in. Then you will have to use a putty knife to remove the old outside seal and caulk. After you get the window put back in then run a bead of caulk around the window top and sides and leave the bottom open for drainage. I pulled a pickup truck with the tailgate down backed up to the coach. Then we stood on the tailgate to do the work. Makes a nice two person work deck. If you take it down to Searcy, Arkansas they can give you pointers on sealing it. There are kits you can buy to do it yourself too. Mine was so bad that if the sun was just right I couldn't see my mirror to back up. When you put it back in the seal should cover the same area that was covered before and no unpainted surface will show up.
Ron KB9TF, Fulltime
2008 Tiffin Phaeton 40 Foot QSH
2011 Honda CRV with Blue Ox towbar and brake