If you want to perform auto repairs on your own Gilera RCR then it is usually recommended to own a Workshop Manual to use as a reference in the event you need to know ways to take out a specific part including Wheel Bearing and install it again the right way.
Gilera RCR Workshop Manuals provides certain diagnostic guides on your vehicle therefore if something is faulty it will help you identify what the situation is and how you can fix it. After that you can assess if this can be done by yourself or if ever the job is too big you are able to book your RCR into a suitable mechanic.
Gilera RCR manual