From what I understand the kit is only about $45.
The Hayne's manual (the only thing I have) says to have the car level on four jack stands and attach a cherry picker to the engine and have a floor jack under the engine. Unbolt the four sub frame mounts and lower the engine about an inch to remove the bushings.

I haven't tried it yet, but need to.

76 450sl 230k
87 300SDL 275k