Hey Matt, nothing to add to Joe's reply except that I just had it done last month. Initially, about a year ago, I was having my rear shoes done and thought it a good time for the cables. They were inop and horribly shot. My mechanic discovered that the pulleys were also extremely rusted and seized. I decided to put off the cable part -- until last month.
All in all, fairly painless -- parts through SL Classics were $56 for each cable, and $68 for each pulley mechanism. My replacements were not plastic, however. Labor came to about 3 hours. It's nice to have the e-brake again (although I rarely use it...) Hope this helps.
James
63 230SL