need help with three main issues!

[flatyre]

hey everyone I just just bought a 1998 1.9d for parts. Basically my everyday berlingo had the wings replaced in the past with cheap aftermarket wings which are full of rust. However the donor van is in pretty good shape so I've decided to fix it up and put it back on the road as a backup van. There are a few problems that need attention first, so any advice would be greatly appreciated. First problem is the rev needle shoots up when the ignition is turned on. Sometimes it falls back down then back up, other times it fills the clock and stays there. Secondly, the airbag warning light flashes continually, and thirdly, both door windows are jammed. The previous owner broke both winder handles trying to free them up, and even using vice grips on the splined shaft didn't work. I removed the glass and mechanism from the drivers door and checked all the cables which are free. So it looks like the main part is seized, so how do I remove the two spring loaded cables and can I buy new parts or do I need to source the whole mechanism? any help would be great.