I always make it a habit to replace gaskets...even the o-ring types as used on the Thruxton. According to
Bikebandit, you will need 4 new o-rings at $7.60 each (a little over 30 bucks). Thats a pretty good deal considering you probably will not have to mess with them for a long time. The insulators are probably fine for re-use, but they are only $14 each (if needed for your machine).