I DID IT! On my beautiful W124 1989 300E (105,000 miles) the belt tensioner unit was shot and I had been planning to do the work for a while. I'd bought the parts through PartsShop (if anyone hasn't ordered stuff from them yet, WHAT ARE YOU WAITING FOR?!?!?) and was waiting for the "right day". The belt was wailing and I kept getting these "if you've got such a nice car, why don't you get it fixed...?" looks.
In the mean time I had done a transmission service on my wife's car ('92 190E 2.3 W201)and ended up over-torqueing the pan bolts and ruining the gasket. Ended up less than a week later having to have the car towed 40 miles ("over the hill from San Jose to Santa Cruz) when the pan gasket failed and spilled most of the new Mobil 1 synthetic ATF all over the parking lot at my wife's workplace. Our mechanics LOUDLY told me never to use ANY synthetic in our cars and said that I was lucky not to have ruined the transmission by botching the job... Needless to say, I was gun-shy in a BIG WAY!
For this reason I kept putting off the tensioner replacement. Yesterday I took a day off from work and made up my mind to do the tensioner job. I'd printed up numerous accounts from this board on how to go about it and I'd printed up the directions from my service and maintenance CD-ROM so I thought I had it in hand. We also have an extra car right now so I figured that I didn't have to rush it and could walk away from it if the thing really got the better of me.
I took my time, looking into all sorts of stuff while I was "in there" and after 5 1/2 hours turned the key - silent, smooth rock-steady purring, just like it should be. I DID IT! I've got to say I had begun to question my ability but as I said, I took the time, made sure to do it right, had the instructions and all of the parts I needed and just got into it.
If you're contemplating a job to keep up "your baby", take your time, have everything in hand before you start and GO FOR IT!
Thanks again PartsShop for saving me around $150 for the parts alone over what the dealer quoted me for this job.

Congratulations! Sorry to hear the transmission work you did didn't turn out well the first time. I know I've done stuff like that many times and it is frustrating. Fortunately you have learned from it and because you have posted to this forum so have many others. I'm glad to hear that you got right back up on the horse and that it worked well with the tensioner.

Happy New Year

Way ta go Jay....Happy New Year...

Super!
Now, did you photograph and document the process so we can produce a DIY article???
That would be nice.

DOH!! WHY didn't I think of that?!?!?!? I have a digital camera in the trunk of the car that I use for business... it would have been SO EASY.

I guess that I was too focused on the project (getting it right, following the instructions, not having any left over parts etc.) that I didn't think that far ahead. Besides, I didn't know that somebody like me could put something like that together for the list. Can we?!?!?

I also want to say thanks to Bill Wood from MercedesShop for encouraging me to go ahead on this. I'm a fairly good DIY mechanic but had something go wrong recently on one of my "jobs with good intentions" and was quite gun-shy. Bill encouraged me to take my time and go ahead - result??? I got it back as good as new and my car sings its' symphony once more. No more squealing belt in the morning or leaving work in the afternoon.

What's wrong with synthetics in a 1989 MB?!?
I've used synthetics in my '86 535i for 70,000 smooth and happy miles (Mobil 1 engine oil, Redline ATF, and Redline diff. oil).