Nope, there was not pressure in the hose's when I did mine. I little residual, that is all. If you do not have the Click-R collar pliers to remove the hose clamps, you can use a small 1/8 flat head screwdriver. just put it into the gap you see on the hose clamp and give it a twist, it will pop open. Then use some bent kneedle nose pliers to reset them. You will hear an audible clamp when they seat. I have now purchased the pliers from Mac tools, $30 if I remember correctly. You might not get fuel out of the bleed, I did on the first filter, but not on the last. Jeep started up with no hesitation anyways.
Also, the upper filter on the water sensor leaked the first time and I have heard here than others have had the same issue, I applied a small amount ot Hylomar (a liquid gasket for fuels and oils) on the upper "O"ring, no leaks. If you use a bleed hose, I believe it is a 1/8 ID hose, and hold on to it, if you don't it will wip all over spraying fuel (don't ask how I know that). When installing, make sure you have the filter correctly positioned in the holder, makes it easier to attach the hoses and wire connector.
There is a ground wire on the back L/H attachment screw, I believe that is the ground for the glow plugs (correct me if I am wrong Merlin) make sure you do not forget it and just check it for corrosion to make sure you have a good connection. I read some articles that this could be a cause of some premature glow plug issues.
other than that, like the others have said, it is very simple and quick.
2008 CRD QDII, OME HD, Pintlers wheels with 265/70/17 Goodyear Silent Armour's, Jeepinbyal UCA's. 4XGuard Front guard, Side Guard, belly guard, Matrix HC. GDE ECO Tune w/ delete.