which plastic bit has brocken?
when mine went it was the white bit at the top of the window guide.
but your best bet it to try your local scrappers, got the whole mechanism for £20 (motor, cables, window guide...), they are about £70 on
if you take it out your self, do NOT alter the cables, they are under rather a lot of tension, so it would be hard to re-attach them.
but if you do remove it, you will be able to understand how it comes out, just make sure that you remove all the parts that are to do with the window.
oh and theres a single plastic clip, that secures the window to the guide runner, keep that, incase one breakes