If you choose to carry out repairs on your own Vespa Granturismo then it will always be recommended to have access to a Workshop Manual to keep just for a guide just in case you want to know how you can remove a specific component such as the Gearbox and install it again accordingly.
Vespa Granturismo Workshop Manuals gives you precise diagnostic guidelines for your car therefore if something is playing up it will help you find out what the issue is and ways to fix it. After that you can determine if you can do this by yourself or if ever the job is just too big you can actually make a booking for your Granturismo right into a trusted friendly mechanic.
Vespa Granturismo manual