Printrbot Simple - Wooden Extruder Upgrade

I've had a multitude of little issues with my late 2013 Simple's extruder and decided it needed some work...

My filament would randomly walk out the side of the hobbed pulley, even when not jamming. I discovered 2 problems:

1. The filament had no guide on the way into the pulley. This would allow it to enter from an angle, and aide in the filament walking. For this, I took the design of the middle wooden piece of the extruder "housing" and I extended the top and added a guide that would on