On Tool has very low prices when I was comparison shopping, plus the fact that they'll pay shipping for orders over $50 lowers the price even more (they say free shipping is for a limited time and I don't know about a heavy tool). I did not shop around for you to give you the lowest price - I just went to On Tool ( I was looking for another tool anyway) and looked up strut compressors. Like I wrote, call them for more info.
A tip to your friend when they remove the struts - mark their mounting position on the car so that when they are re-installed they will be close to the original position. This should make the alignment close to what it was before removing the struts and less wear on the tires when the vehicle is taken for an alignment. The alignment should be the first thing that is done after the struts are re-installed. I've seen mis-alignments after front end work (struts included) that ruined tires that were driven for only a few miles
I've rented the spring compressor from Performance Products when I rebuilt the entire front end on my 300D and replaced the rear springs. However, the PP rental tool fits inside the spring after removing the shock absorber. A strut, on the other hand, is inside the spring and a strut compressor is needed to compress the spring to replace the strut. A strut is a shock absorber, but it is also the mounting point for the spindle, backing plate, brakes, wheel, etc., etc. and it takes the place of most of the components comprising conventional/traditional suspension components. When a strut is removed from a vehicle it comes off as an assembly after removing the wheel, brakes, etc, and then the fasteners at the top and bottom mounting points to the car (there are different ways the struts are mounted and things mounted to the struts - I am only talking in very general terms). Then a strut compressor is used to compress the spring, the spring holders/fasteners are removed, the spring is removed from the strut, and then the strut can be replaced. I do not see how the PP rental spring compressor would work on any strut that I have experience with (perhaps another member knows of struts made that you could use the PP tool on). I totally agree with you, I would not even try to compress a M-B spring without using the PP rental tool or something similar - those springs are much stronger than what is one other vehicles and serious injury even death could occur if the wrong spring compressor tool is used.
Hope this helps!
P.S. Sorry ke6dcj I was talking about the back springs on my 300D having the shock in the center of the spring. The front spring does not have a shock inside of it. Oh Well!