You will need to remove the front which you should be able to do by inserting a screw driver or putty knife in the gap between the top and the front near the edges and releasing the clips that hold it on or by removing the two screws at the bottom that hold it on.

Here is the service manual which should show you how to do everything.

http://www.servicematters.com/m...ibrary/docs/16008714.pdf

Be sure to clean out everything well, and I suggest you replace the rollers and idler tension and any other parts you see need replacing at the same time.