Had to cut out the seal, then the vent then slid out(theres a notch in the window lip)
When I removed my rear vent windows:I found them badly rusted out at the bottom!
-thus the body was rusted also.
needed: rust inhibator, filler etc
I opted not to put the vents back in--seals were too$$$$.(I replaced all seals) put flat glass in its place.
Hope this helps
Good Luck