Re: 1987 model 300E transmission service
I'm certainly not an automobile mechanic, but I have always gone with the bedrock principle for cars: "If you buy a used car and don't know if it's been done, then do it!" I just bought a 190e a few weeks ago, and had all of the fluids changed except for the power steering fluid. I've never heard of a transmission service damaging the transmission. If you change the fluid and the gasket now, then you'll have piece of mind and won't have to worry about it for another 30k.
I have been told by several MB mechanics to RELIGIOUSLY change the brake fluid every two years and the antifreeze every three years, regardless of mileage. If you don't know the history on these two fluids, I would suggest getting them changed too.
The transmission service would be the most expensive (around $130 I think), but the others are not too bad. A small price to pay for peace of mind!
I hope that this was help for you Marvin. Take care.