No heat required,as it's just an ally split DU bush...
once the gear lever was removed from the bike,I used a socket with outside dia. just under 14mm to push out the old bush with slight hammer force.
Fitting the new one I used a long 12mm socket head cap screw, lightly greased the new bush on the outside,inserted the new bush into the socket screw all the way,insert the socket screw into the gear lever and position it until you're happy that its fairly square, and then gently tap the socket part of the screw to insert the bush.
remove the socket screw,grease the inside of bush which is now firmly fitted into the gear lever and you're ready to refit it to the bike.