Did my 2010 E550 drain, filter, fill. Used Meyle filter+gasket, and Shell ATF134 as specified. New aluminum trans pan bolts.
It was pretty hilarious; I could not get the fill-tube in the pan loose, so I was going to drop the pan hydramatic-style. Well, things got caught up and I had a used trans fluid shower. That meant fluid coming out didn't measure because all that stuff is now on the shop floor, and I had a great time filling, overflowing, running, and re-filling the transmission. I ended up using twice as much fluid as I should have (like over 8 qts), but I suppose the good is that more of the old fluid came out than would have otherwise. I am sure glad it was on a hoist for all that.
Lessons:
1. Drain pan overflow tube, get it out even if you break it, it's why you replace it.
2. For the red fluid 722.9 transmissions, they're not kidding about the service interval; they'll cook the fluid on an E550, mine was brown at 20k miles over (last changed at 50k by dealer per the record, this change was at 120k miles).
3. You'll want to change the filter/strainer.