There is a thread on how to do this for the older w124 (1986-1995) 300E at http://www.mbca.org/pages/tech/MBCA_Remove_dash_vents.htm .

However, I don't know if this will apply to your 1999. And if it does, won't that just get you into the air duct, and not really behind the dash to get to the grill? Most older MBs have a dash instrument cluster that pulls out with special hooks. (Sold at Fastlane, above, or your MB dealer)

http://www.peachparts.com/shopforum/showthread.php?threadid=26838&highlight=w210+instrument

http://www.peachparts.com/shopforum/showthread.php?threadid=14144&highlight=w210+instrument

http://www.peachparts.com/shopforum/showthread.php?threadid=20439&highlight=w210+instrument

__________________
John

2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)

Click to see 87 300E