Adding to what you've said above, I found this Gearwrench set speeds up the replacement considerably. They are the only company I've found that makes a ratcheting box torx wrench.

9224D 4 Piece Double Box Ratcheting E-Torx® Wrench Set - Gearwrench

Count on GEARWRENCH to get the job done. Get the 9224D 4 Piece Double Box Ratcheting E-Torx® Wrench Set here.

www.gearwrench.com

I had to remove my '08 S550 alternator twice! Once to replace the alternator and the second time because the timing chain tensioner bolt needed to be retorqued! Replacing the alternator is a hateful job, especially if you have meaty mitts at the end of your arms.

 

I saw that one but here's reality, (should have included this in the notes) once you break it loose, you can use either a 10mm or 3/8 ratchet box end to take it out or put it back. You just can't use it to loosen or tighten it. Anyway I found that underneath the best way of moving the bolts were with a mini 1/4 ratchet and the 3/8 socket. Once you tie wrap the hydraulic hoses out of the way, the front is easily accessible. The rear one, you can fit in the ratchet through the back of the control arms but it's a bit of a tight fit. Amazing how they make it so much work to pull the alternator lol

 

Don't buy a cheap replacement, get a brand new Bosch so you won't have to worry about it again for a very long time. A previous owner replaced an alternator in my SL55 (!!!) with a Duralast from Autozone. Terribly stupid thing to do. It fizzled one day and began putting out 30 Volts, caused all manner of havoc and burned up a few expensive parts. All to save a few hundred bucks

 

You have to be careful with aftermarket parts for this vehicle. I am lucky to have a very qualified reliable rebuilder close by, he had one ready on the shelf. Much cheaper than online or even an aftermarket new one