i am not very automotively inclind...but today my service consultant at Rusnak Pasadena said that i needed to change my distributor cap and motor (it might be rotor...i'm not sure...sorry if it makes a difference)...anyways...he said that it would cost around $400 because its a big engine and the parts are from Bosch...to me this sounded a little too expensive so i was wondering if thats a reasonable price...i am truly sorry if my description of the service required does not make sense...if it does not please reply and i will call him and make sure...please advise...it is a 1995 S500....thanks....

Yup, I think he meant rotors! Your car has 2 caps & 2 rotors, and they are NOT inexpensive. Further, they are not known to last particularly long on M119.xx motors. How many miles does your car have? Knowing that will help us better opine.

But you probably do need to change them...there's a great article here on the site to guide you through, check the "Do It Yourself" tab at the top of the page.

thanks michael for the help...my car has about 60,000 miles on it...i don't drive it much thats why its almost seven years and old and only 60,000....hope this helps...

I'd change them, essentially as a maintenance item. They do wear out, and there have been upgrades to these parts since your car was new.