If you choose to do repairs on your own Vespa GTS 300 Super then it is always a good idea to have access to a Workshop Manual to keep just for a reference if perhaps you need to know easy methods to take out a specific component including Wheel and match it again correctly.
Vespa GTS 300 Super Workshop Manuals are able to offer special diagnostic guidelines for the automobile so if something is not working it will help you figure out what the situation is and tips on how to resolve it. Then you are able to decide if you can do this yourself or in the event the job is simply too big you can actually book your GTS 300 Super right into a decent mechanic.
Vespa GTS 300 Super manual