If you have to perform maintenance tasks to your Moto Guzzi V 50 C then it is usually a good idea to have access to a Workshop Manual to use as personal reference in the event that you want to know ways to take off a particular part including Gearbox and match it again in the correct manner.
Moto Guzzi V 50 C Workshop Manuals gives you specified diagnostic guides with regards to your car therefore if something is not working it helps you understand what the issue is and methods to repair it. After that you can evaluate if you can do this yourself or if the job is simply too big you are able to book your V 50 C in with a trusted repair garage.
Moto Guzzi V 50 C manual