As far as I understand it they have a spring loaded metal pin in them so you cant just route them out and replace.
my thoughts.
- take out he grub screws, DUH!!!
- use the router to do a really shallow cut over the plug, removing the glass and the top of the plastic and then get a battery drill and drill around where the pin is and dig it out.
- then use the router and router guide to remover hte plug as normal
- then install the plug making sure its the same cant as the opposite fin.
anything I should consider