If you need to accomplish fixes on your own Vespa GTV then it will always be a good plan to possess a Workshop Manual for a reference in the event that you want to know how you can remove a specific component for instance the Drive Shaft and match it again perfectly.
Vespa GTV Workshop Manuals will give you certain diagnostic guides with regards to your vehicle therefore if something is wrong it can help you ascertain what the problem is and methods to make it better. You can then evaluate if you can do this on your own or in case the job is too big it is possible to book your GTV into a trusted repair garage.
Vespa GTV manual