Below please find a few notes from driver window replacement on a 2005 S500:
* Only tools required are star wrenches
* To remove the old window drop it down until you see the star screws (two) (see picture) on the bottom of the door body
* The glass gets removed from the top, and replaced from the top
* loctitie blue is recommended for the star screws
* only the bottom of the door cover needs to be removed, leave the top in place as not to disturb the butal black sealer
* glass sells new at MB dealer for $400 USD, plenty of used windows on ebay for under $100 USD delivered. If buying used, try to buy a later year with low miles, the unit that holds the mounting screws to the window due wear over time and prevents the window from a secure seating in its mounts.
* fairly straightforward on man job, should take about 60-90 minutes