[snapdragon]

No need to depressurise.
I have disconnected mine and nothing to notice came out that a sheet of kitchen roll wouldn't catch.
Diesel/liquid is not compressible, so there is no 'spring' effect like there is with a gas.
I think it should cope with not being bled as you are not removing the pipes from the jectors are you?
If it has got empty pipes, you can crank with the metal pipes on the injectors cracked undone and crank and then stop cranking when fuel comes out and nip up it should then start and run rough.
In any case, try not to run the high pressure pump dry on it's inlet side.
Another bleeding point is the top of the fuel filter has a nipple on it with a bolt in the top - you can attach a vacuum pump or pela type oil extractor here..