If you have to perform fixes for your Vespa GT60 then it will always be recommended to possess a Workshop Manual for reference should you need to know the best ways to take out a certain component for example, the Gearbox and install it again correctly.
Vespa GT60 Workshop Manuals can offer you targeted diagnostic guides on your automobile therefore if something is wrong it can help you ascertain what the issue is and the best way to correct it. You will be able to analyse if this can be achieved on your own or if ever the job is simply too big you can book your GT60 in with a suitable mechanic.
Vespa GT60 manual