Slide seal replacement

[audio1der]

Our larger/main slide has a leak; the carpet inside is wet every time it rains when the unit is in storage (slide is closed).
I brush off/squeegee the slides before pulling them in after EVERY trip, and never once have we closed either slide with a branch or something foreign in the way.
A mobile service tech stated our upper slide flange seems to bow out as if it was closed on a branch, and doesn't seal against the rubber seal around the perimeter of the inside of the slide flange ()-shaped rubber.

Is this as easy to replace as it seems? Remove old seal, thoroughly clean flange of old adhesive residue, apply new seal? It hardly seems worth the $500-600 of materials and 2 hours of labor (he did quote on the high/worst case side).
I know a parts manager at an RV center so I should have access to the same material the mobile tech would use, at a discount.
The inner/outer sweeps are conditioned regularly and are in fine shape.
In the attached photo, the seal is on the right.
Thoughts?

[bobbecky]

You might check the seal around the window, I guess you have a window in the slide. The seal can have as little a gap as a sheet of paper may not fit, but you will get quite a bit of water inside. We struggled a couple years ago with a leak, and it turned out to be the window seal. I did not have the time to remove the window and replace the sealant material, so I put a small bead of silicone around the window, and haven't had any leak since. This is the seal between the flange and the outside wall of the slide.