I wasn't sure what mine was held in with. My door is from Lippert components and they used silicone. (Maybe that's why it leaked):)
Called RV glass place that did work on my cab window in class C. Asked them what to use. Here is what they stressed.
Clean out all old silicone, and that can take a long time because you have to get ALL old silicone. Worst part of the job. New silicone must be what is called "100% silicone". They like what Winnebago has been using for years. Nuco or Nu-flex 331
http://www.amazon.com/Nuco-331-Silicone-Nozzle-Odorless/dp/B00OJJK2IS And I paid $17.00 for a tube. Cheaper on-line than buying in person at RV place.
After getting the groove clean as possible, wipe with alcohol pad and look into groove and you'll probably find more little tiny bits of old silicone. If so, keep digging it out until you don't see any left over old silicone at all. Again worst part of job but all old silicone must be gone. Then put new silicone and let dry couple days if possible. Then before putting window back in, to make sure there are no leaks. Lay flat outside up on picnic table or something and fill with water up to the plastic ring. Water should not run or drip out. If it does you have a leak and best to start over.
Took me about 2 hours to get out all old silicone. To fit the weird size of the groove, I used a drill bit as a scrapper along with popsicle sticks.
I think if I had to fix it again...Dicor wouldn't be out of the question. But would still be stuck removing silicone, which is the biggest hassle of the job.
2003 Majestic 23P... Northwest travel machine
2013 Arctic Fox 25W... Wife "doll house" for longer snowbird trips
2001 "The Mighty Dodge"... tow vehicle for "doll house"