300-24, saloon and coupe, E300 24 valve diesel estate
Open bonnet
remove chrome grill frame (4 screws at top)
remove 3 screws from each side of the grill on the inside
gentley remove the plastic grill
reinstall is a reversal of the process
You'll need a new laurel-wreath emblem as I can guarantee that it'll break when you unbolt it
Basically, undo the bolts that hold the entire chrome grille onto the bonnet (possibly four 8 or 10mm ones). Once the grille is off, you need to remove the laurel wreath badge on the front (easier if you remove the star motif as well), then remove the countersunk cross head screw from the bottom of the surround, then remove the sprung metal clips that surround the edges of the grille insert.
Once these are removed, the grille should be released and you can remove the plastic insert.