oh no, its a real hassle when this happens.
you can replace the entire mechanism, i believe haynes shows you how to do it. in theory its a simple matter of removing a few bolts, but in reality its difficult to get the mechanism off once the bolts are removed. a scrapyard mechanism wont cost much, but make sure you use some silicone spray on the rubber runners to stop it happening again. all windows should be lubes every year. DO NOT use any oil based lubricant, only silicone spray (with ptfe if possible)