That actually looks like the wiper, not the inner or outer slide seals.
Mine are glued in place they use a serious contact cement and clean the surface extremely well. I looked on-line and saw some that are glued plus some that are glued and screwed. Not sure on your rig.
Mine have stayed on since 2008.
I will not comment on the labor quality of the two places that "worked" on your rig. But, rest assured I do have my opinion...
Yes, you can do it yourself - call Tiffin and get the correct wipers (or go to their on-line parts store). If you call, have your VIN number handy and they'll find your's pretty quickly.