If you wish to accomplish fixes on your own Piaggio XEvo 125 then it is usually a good idea to have access to a Workshop Manual to keep just for personal reference in the event you need to know methods to remove a particular part much like the Gearbox and match it again successfully.
Piaggio XEvo 125 Workshop Manuals will provide you with particular diagnostic guides for the car therefore if something is wrong it will help you work out what the problem is and tips on how to resolve it. You will be able to evaluate if this can be done yourself or if the job is just too big you can still book your XEvo 125 into a nearby garage.
Piaggio XEvo 125 manual