I am in the E class forums and that engine is also in the E550. As others said, lots of people like to try special exotic oils thinking it's better but lots of us just run Mobil 1 or Castrol and it's fine. It doesn't really care too much about oils as long as it's on the approved list. Occasionally you hear of weird engine issues and then it turns out they used regular 10w30 that wasn't on an approved list. But they did other wacky stuff too so it's hard to say. That's why I'd just stick with approved oils, Mobil 1 is what they sell at the dealership although it's 5w40 and it's extra expensive.
As for that site, it normally works all the time, I'd try it again later, maybe next week, not working for me now, their certificate must have just expired.
There's also several youtube videos on doing the maintenance to that engine. The oil separator is reverse threaded so you have to turn it the opposite way to loosen/tighten it. Other items on that engine is the thermostat tends to go early and the tensioner/pulleys go too. If the thermostat goes, I'd replace both pulleys/tensioner/belt at the same time as one of the pulleys has to come off anyway to replace the thermostat. Also check around the oil cooler gaskets for leaks. Then MB is also well known for having bad motor mounts that go early. Mostly because they're liquid filled so it's really smooth and quiet when they're good but you'll feel the vibrations when they go. If you have a leak in the CV boot, be careful with aftermarket CV joints, some are not good. Otherwise have fun with it, been driving my two M272 engines for the last 5-7 years.
Transmission fluid is Shell ATF 134 which you can get a case of at the shell distributor for around $60 for a case of 12 quarts. I haven't priced it lately so it's probably more now with inflation but the dealer always charged $20+ per quart.
Looking to buy Shell lubricants or oils? Use our distributor locator to find a quality approved distributor who can supply the Shell products you need.
www.shell.us
Also FCPeuro is a good site to get parts from, lifetime warranty on all the parts they sell. Sometimes with brake parts it makes sense to get it from them, other stuff like Bilstein struts which have a lifetime warranty anyway might be cheaper at a place like rockauto.com.