As far as I understand it they have a spring loaded metal pin in them so you cant just route them out and replace.
1. take out he grub screws, DUH!!!
2. 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.
3. then use the router and router guide to remover hte plug as normal
4. then install the plug making sure its the same cant as the opposite fin.
anything I should consider