Whatever you do don't force the key in there. If you were to get the key in there and not be able to get it back out again without being able to turn it to position 1 or 2 (I forget which) , you'll be in a world of hurt. Consider yourself lucky! Search under "tumbler". You''ll need a new tumbler from Mercedes that will require reg and ID. Probably around $100 now. Then you'll have matching keys to ignition, doors and truck. "V" shaped tool, each leg about 6" long, is made from coat hanger wire. Directions are probably in the archives somewhere. Get the tumbler first and you can see how the tool will depress a spring clip. Your tumbler will probably come out in two pieces.

glenmore
1991 300CE
2000 C280