Hi Spawn welcome from New Zealand.
Before you go spending a fortune check the rocker gasket closely as others have said.  Also the oil breather is at the back of the motor.  It runs on a pipe up to the airbox.  If you have aftermarket airfilters (like K&N's) under the chrome bearclaw a small filter is usually fitted to this breather.  The breather tube may also be cracked.
I have a filter on this and my bike gets a buildup of oil over time around this area, I clean the filter, degrease and clean area
Unless you can physically see it leaking/flowing out i'd recommend closely monitoring it.  I have no faith in dealers fault diagnosis/abilities but big faith in their ability to remove money from me.