It turns out that the leak on the pump is from the nozzles, which does not require a rebuild or taking the pump off the car. The first mechanic I went to, who offered to do the job for $330 estimated the job would take 3 hours, and only involved the six seals which need to be replaced.

Today I went to a Mercedes specialist who would do the job for $400, but mentioned that included in this would be replacement of certain hoses, as well as installation of new fuel filters. He said that whenever you do this fix you need to install new filters. Moreover, he wanted me to leave the car the whole day, and that fixing the pump required the removal of a number of parts on the engine.

When driving my car, he did notice the slight shake or shudder when I come to a stop, and explained that that was likely due to air leaking into the pump, which I thought a good diagnosis.

What do you guys think?