Electric window mechanism faulty

[adamskibx]

Its time to get this sorted-When making the drivers window go up and down, worn out coggs on the winder system (not the motor bit) are causing the window to get stuck and make a horredous racket. I need to replace this cog bit but dont know what the best way to approach it is- will the glass need replacing or can the bit be replace without going to such extremes. Cheers, Adam