I took a vacuum in for service recently and requested to only have a part fixed. They did a full service on the machine that cost about twice as much and didn't deduct the $10 coupon I had off the bill either.
I have no qualms about the service itself. The vacuum is fixed and was cleaned (and whatever else is included in servicing).
Beware of what service you are getting, I thought I had made it perfectly clear that I wanted only the part replaced. I guess that's what I get for not being a stickler and confirming every detail. :(