Primed 3 times as per Guzzle's instructions. There is fuel in the bowl as when I open the drain it drains out - I have a hose and tub underneath to catch the diesel.

Guzzle's instructions said it was possible to do it in situ, but easier if you take it out. I also got the full seals kit which included the Vibra-lok seals for the head-flow pipes, inlet pipe, and fuel return pipe. Once they're all off then it's only 2 bolts to get the bowl out.
Once out it is really easy to inspect and clean. The biggest pain was getting the old Vibra-lok seals out. The one on the fuel return was really wedged into the brass fitting.