Guys - I made the rounds on this one a couple of years ago and could not find a split boot for a 240. There are lots of split boots out there for other models.
I also heard over and over that split boots are no good. I do remember using split boots on VW axles way back in the past somewhere and not having any trouble, for as long as I had the car anyway.
With many axles you can undo a clip on the axle shaft and take off the inner cv joint and slide the boots off and replace them, but not with this axle.
I was surprised to find no one in the Athens Ga area, including the Mercedes dealer, who was able to renew the boots.
So, I went with a rebuilt axle with new boots and a lifetime warranty.
It isn't difficult to change out the axle but you do have to drain the differential and undo a plate to get to some clips that let you withdraw the axle from the differential.
You could check the parts shop on this site for an axle. Also call your local dealer and see what their take on boot replacement is. The dealership here has some nice people but I wouldn't accuse any of them of being exactly cutting edge on tech stuff.

No special tools needed. A Haynes manual explains it well enough.
Good luck and ask around some more,
Harvey