Try the Search feature at this Tech Help forum as there are tons of headscratching discussion on transmission and vaccuum, most of the time interrelated.
It takes methodical tracking down of causes, usually several.
Sometimes it's a simple fix, other times it takes a lot of patience and time.
Some have mentioned just the simple act of changing the tranny fluid and filter improved the situation, others had to deal with oil contaminated vaccuum lines that resulted in other problems besides shifting.
There are also plenty of opinions out there on what to live with in the MB automtics (harsh vs. smooth shifting and the tradeoffs on longevity of trannys.)
Since I don't consider myself an expert on this subject but have dealt with many quirks of the transmission, my recommendation is to peruse the search results and pick your way through the information.
One more suggestion is to visit: http://www.mbz.org/resources/articles/trans/
This site gets down to the nitty gritty of shop talk.
Even if you choose to feel comfortable farming out the work to a shop it certainly doesn't hurt to be better informed as there probably is plenty of misdiagnosing if you stumble upon the wrong shop or an apprentice ends up practicing on your car.