Better replace the fuel filter and drain the fuel separator while you are at it. Thats assuming you want to continue driving your new toy, I mean vw.
The top part of the pump handles the pumping of fluid from the tank to the pump, the bottom and rear part handles pushing it into the engine. THe veins in the top part are easily soiled by the wax and sludge that comes with diesel powered vehicles. You can over come this by using an external fuel transfer pump. The lower end when its worn just needs remachining.
Your mpg is low. You should see no less than 49 driving it like a rental car. 60mpg doing all the eco stuff here. Of course back in the day the top speed limit was 55 in VA.