I had the same part replaced recently...it comes complete (no choice) and it's puzzlingly expensive! (350$cdn)...especially considering a new blower motor was only 200$

The thing to be aware of is that there are different variations of of this regulator on a 300E, I was told, ( natch mine was the $$ kind) and the other variants are quite reasonable (1/10th the $$$) Check it out, first.

CB