Took our 2003 C230 Kompressor hatchback in for it's B service and the dealer says we need a new "engine" vacuum pump. But as they explain it, it's really an electrically driven pump since this four-cylinder engine is supercharged.

How hard is it to replace this pump? Wife says the HVAC is acting up and I presume erratic suction is the reason.

I'm a good mechanical guy, but I can't find a manual that explains anything on this car. Where is this pump mounted? Is it something that I can replace? The dealer wants $400 to do this job.