Richard:

I don't know specifically about a W126... I have a 97 C230 and the front brakes were the easiest I've ever done.. very straightforward...

[obviously] secure the car on jackstands > there were two bolts secureing the top part of the caliper > remove and rest the caliper on top> the pads were then exposed > remove the old pads > insert the new ones > you'll probablly have to compress the caliper piston back into the caliper >> I used a large C-clamp for this > make sure the brake resivoir top is open and that hte fluid does not overflow.. insert new pads . secure the top part of the caliper > and done.. >> and seat the pads before driving >> pump the brakes..