It doesn't matter if the dahl/racor is completely full of fuel. Both my Westerbeke and Volv0 diesels have the racor filters before the lift pump. No problems so far.

When I change the racor (dahl in your case), I close the fuel line valve, open the filter, remove the element and replace it, top the filter up with fresh diesel and close it up. To make sure the system is purged of air, I pump the manual pump until it firms up. The engine starts right up then. Another tip if you get air into the injector pump is to put the throttle wide open and then crank the engine over until it starts. Having the throttle open puts a lot of fuel through the injector pump quickly and purges the air much more easily than bleeding injectors while you have the engine ctanking