Try a search - I did a write-up on this last year. It's a long and fiddly job, but very definitely a DIY job with a tea-break and a box of plasters for your knuckles.
I got my plugs from GSF I think. They were about £50-odd quid for Bosch platinums.
I read elsewhere that it's easy to strip the threads - having had that done by dealers on 2 cars (neither MB) that I've owned in the past, you might want to weigh up the risk of DIY.
Sorry, after failing to attach the pictures to the post I didn't keep them. as for the torque settings I just seat the crush washer and go a quarter to a half a turn more. as long as you relise you are meant to crush the crush washer, not flatten it, you'll be fine. or go here