I replaced the front struts on my '87 300D with csnow's procedure. The key is to put the jack at the end of the control arm like he says. Its VERY dangerous if the spring should break free. If the jack slips, there is a decent change the control arm bushings won't allow enough deflection for the spring to fly freely (at least when they are relatively new control arm bushings). However, be careful and don't stand in front of the spring just in case!
Check your upper strut mounts and make sure they're not cracked. IF they are, replace them at the same time. ~$45/ea.