300D ignition tumbler how do you replace it?

Answer 1

Since you say it is a 300D i will assume it is a W124 body style.

You will need a wire tool... here is how to make it.
You need 32cm or more or 2mm thick wire. Welding rod works great.
at 6 cm bend 90 degrees 2cm bend again 90 degrees . you now have a squared off U shape
Cut ends even with each other and file off to a 45 degree cut with longest part to the outside.

You must remove the black trim around the ignition.
Get the key to turn to position #1
Slide a the wiretool into the small holes now at 1o'clock and 7 o'clock positions (or there abouts)
Pull lock out using key.
Put key into new tumbler
Turn to position #1
insert into hole
remove key
reinstall black trim.

Answer 2

good luk man..with all the new anti theft stuff id let a pro do it. sorry i cant help