Welcome, Derek! We, too, have a Trillium
Outback, older than yours (2004). Our driver's side window in the dinette area, which for us, is where our heads go, actually popped out on us! It was totally our fault, as we have a habit of resting/leaning against it somewhat when watching movies on the computer....and it is, after all, the emergency escape
window. Once we tried to re-insert it, it leaked. So out came the butyl tape...
It wasn't a difficult job at all. But it will go definitely ALOT easier with 2 people. One outside, one inside. Trying to do it solo might make an amusing YouTube video but would NOT be good for either your mental sanity or your desire to attempt the remaining windows!!!!
As to the comment regarding window weeping holes, on these windows it is very important to keep the weepholes clear. I do it at the start of each season and sometimes, if I remember, before we put 'er away for the winter. I use a 6-8" piece of uncoated wire and feed it in thru the weep hole. You might be amazed at how much dust and debris is removed! Those little weep hole caps that (should ) cover the holes help alot and can be purchased very cheaply from Team Trillium in Calgary.
We also ordered a new gasket for our door from him (Joe Thoen), as ours split from repeatedly being stepped. That, too, was very reasonable.
It simply slides over the fibreglass edge.
Now, unless your window at the back is totally different than ours, which is solid and doesn't open, these same principles apply there, too. Does your back window open? If so, I am extremely jealous!
Good luck! It's a great little trailer and better still once you fix those leaks!