420 sel

Hi, I have an oppertunity to purchace a 420 sel at a great price from a dealers lot.
However the car is not running at this moment. When the dealer got the car all the spark plugs were taken out and he hasn't time to replace them and check out the car so my price is as is. or I can purchace this car fixed at a higher cost.
Now before I purchace this I would like to check the compression (maybe thats why the plugs are gone) can I get accurate compression reading with all the plugs out? or do i have to put 7 of them in?
also I've read about people using starter fluid on these cars.. how do you do that with a fuel injector? I know carbourated models just take a quick hit in the carbs chamber...
everything else visually looks great new brakes, tires exaust, suspension.148K orig miles, inside's nice just a few normal wear and tear front seat cracks.
so any ideas?
thanks, Jeff