You need a tool to pull the pins that hold the rails in the cylinder heads. Here is and example.

http://cgi.ebay.com/ebaymotors/Mercedes-Benz-Guide-Rail-Pin-Puller-Remover-Tool-1712_W0QQcmdZViewItemQQcategoryZ35625QQihZ015QQitemZ250020805123QQrdZ1QQsspagenameZWD1V

There are also slide hammer versions, but they don't work as well.

There are lots of posts on how to do this.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe