Sounds like a syncro issue to me, or perhaps a hydraulic CSC issue in the making but I would be leaning towards the syncro.
Warranties do not cover wear and tear but only mechanical failure so you may have a fight on your hands.
However if you approach the dealership in a calm and professional, non confrontational manner then you may get lucky.
Warranties and extended warranties usually have the condition that the car must have a full service history.