The manual doesn't specify anything beyond, "use Mercedes-approved
oil."  If I get a quart of "power steering fluid" at Autozone, will
that work ok in the Mercedes?

Reviewing old posts here, they're mixed on using ATF vs. power
steering fluid; presumably they're fairly close and ultimately perhaps
it makes little difference, but I want to do it "right."

Also, the manual says to fill the oil to between the high and low
marks on the little plastic deal, but the only markings on it are
little triangles that run the length of the plastic thing, so I'm
thinking instead maybe I should just pour it in 'til it's up to the
ground area, where the reservoir changes from round to box-shaped?
Dunno if this makes much sense to many unless they know this specific
unit, but it'd fill it to within maybe 3/4" of the reservoir cap.

thanks,
-tom!