I just replaced my FRONT bumper cover last weekend on my '93 400E. Getting it off is a piece of cake -- 5 nuts to remove. The back bumper, as I recall, is similar. Once off, you can take off the black plastic impact strip, chrome, etc.

Incidentally, I painted mine myself. Went to an auto paint store, got 2 cans of bumper paint made by SEM, (in my case the color was dark titanium metallic which matched the original almost perfectly.)