Diesel Bombers - injector replacement question

Ok I am replacing injectors and can't remove the glow plug that is nearest to the firewall on the passenger side. I know there is a lot of fluid in the cylinder and I need to get it out. Since I can't do it the conventional way by replacing the injector and taking out the glow plug and bumping it over a few times, I went out to harbor freight and bought a cheep vacuum pump to remove the fluid. The question I have is do I need to remove every drop of fluid out of the cylinder or is getting 90% of it out acceptable. Because of the location of the injector I am afraid that it will be difficult to get it all. I don't want to seize the motor and I am hoping I can do it this way. The glow plug is very stuck and I don't want to take a chance of breaking it off. I will need to do it eventually but it is not a truck I drive very often and I can't take the time to do it now. I tried taking it out by removing the rocker arm and push rod out and useing the socket to remove it entirely, but it makes a squeaking sound when the gp is turning and at the end of the threads it still won't budge. I figure not using one glow plug wont kill me in the short term. any hints would be greatly appreciated.