I don't know what they would charge to repair it (or how long it would take), but I'd bet that they would send you a replacement lens for nothing. They you could repair it yourself.
The way I do it is to use heat to loosen the bezel. It's best to be wearing nitril gloves when you do this, just to avoid betting finger prints on the lens. If you need to wipe the lens before installation, use a high quality micro fiber cloth. I get mine at office depot. Once you get it open, replacing the lens is pretty much self explanatory. The only other real advise I can give you is to avoid an environment wherein there is lots of lint (or other particles) floating in the air. You'd be surprised at what's floating around, until you get the light back together and turn it on, only to discover all of the crap that made its way into the light.
What I do, when I need to, is to do the actual opening of the bezel in the bathroom. I run the shower with hot water just enough to get a bit of humidity in the air. This greatly reduces the amount of crap floating around in the air. You just don't want the steam so thick that your reflector fogs up.
