Don't use petroleum based oil on the rubber seals. I used liquid dish soap to slide things into place, and waxed heavy twine to pull the gasket over the lip.
Find a helper to press gently on the window from the outside while you pull the twine toward the center of the window. Once it's seated, wash the soap off and check for leaks. A tube of rubber cement with a narrow tip can inject a plug into any holes.
