Dealer Dilemma 1/2 hr. to diagnose drty engine

[lowprof.]

I recently purchased 300E 120K and in my initial servicing/ reconditioning/restoring, I took it to my local MB shop to have the transmission serviced. ( Will do most work myself, but I don't mess with transmission). The transmission servicing was apprx. $125, certainly a reasonable price. This is my problem:

I also asked them at the time I dropped it off to inspect the engine and see if they could pinpoint the origination of the obvious oil leak. (The engine was very dirty and oily, and I have since cleaned it and discovered leaking main seal). Well, I returned and picked up the car and this is what they told me, "the engine is too dirty, make an appointment to come back in and have it cleaned." Charge = one half hour labor. I am not happy with this situation at all. 35 minutes to diagnose a dirty engine!!! I cleaned it and pinpointed the leak in 45 minutes total.

How should I proceed?

Thanks,
Don in Michigan