Mike,

When I changed to synthetic in my transmission it had quite a few miles and there was no leaking problem. I believe this to be because there is no combustion in the transmission causing the nasty contaminants like you have in engine oil. My transmission has never leaked with Mobil One. I indeed would not change my older engines to Mobil One for that reason.

The plug in the rear injector is merely a short piece of that cloth colored hose with a plastic plug inserted in it. ricali brings up a good point about the seals under the injectors, but I suggest that you replace all the cloth covered bypass hose first, then if there are still leaks, replace the injector seals as ricali suggests.

As far as trading it for a Ford goes, that's your personal decision. I get the impression that you are familiar with working on cars, your just new to the breed. I was completely lost when I started working on my Benz diesels, but like anything else you learn as you go. Unfortunately I went about 12 years driving and maintaining them without mercedesshop. I would have ramped up much quicker if there was such a source of information for me early on.

Enjoy,