Stewart,
The tires leaning in is most likely an excessive negative camber setting on the rear wheels. This is typically done to enhance road holding but will also accelerate inner tire wear. I'd have it changed to within factory spec.
Regarding the rear read this
http://www.peachparts.com/shopforum/showthread.php?threadid=71225&highlight=springs
I hope the dealership is covering the fixes. It appears they may be guessing at repairs. Do they deal exclusively with MB?