TDI Frame Driver Seat

Hello.
I have a terrible cracking noise coming from the backrest of the driver's seat in my Passat TDI 1.9PD (05/2000, 70,000 km).
I went to an auto upholstery specialist, and he said that something was probably broken on the lumbar support, and that he would have to replace the entire frame of the backrest. He can reuse the seat cover.
I have the following questions about this:
- Can the ramen installation and airbag replacement be done by myself?
- Is it possible to remove the outer casing myself so I can inspect it and see what's defective?
- Does anyone happen to know approximately how much this frame will cost at a VW dealership?

I've managed to fix the crack in the meantime. If you want to know more, you can read about it here:

http://passat3b.de/phpBB2/viewtopic.php?t=9987