I researched this and the hydraulic unit does not produce the force you will need for the spring. At least the 123 spring.
The internal unit, you can't get it into the interior of the spring. I have one and you can't get it in the spring opening at the top. The 123 has a plate at the bottom so that way is also out.
Consider buying or renting the SIR TOOL of the Klann tool. I know its expensive but after doing the 123 suspension, both front and rear, I would not use any other kind of spring compressor on the springs. I did a 65 Mustang with the internal type of compressor. It was fine. the springs are not that tall and rather weak. The Mercedes springs are quite tall and VERY strong.
Performance Products rents the Sir Tool and do a search on the Klann unit. Some one on the forum is trying to do a Group purchase to get the price down
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car