Advice needed Re Parts for: 2005 Piaggio Vespa 50cc ET2

Hello everyone, I shall attempt to repair a 2005 Piaggio Vespa 50cc ET2 and I am in dire need of advice on which parts/part sizes I need to buy.
It is my neighbours scooter and both he and I are completely un-knowledgable re repairing Scooters.
The info I have received on the scooter from and according to its owner is:

It is Un-Restricted.
It has never been serviced.
It runs and reaches 50 after that it loses power.
He tells me that the cylinder was bored to 80mm.(whatever that means).

I now need to know:
1) Which size of Variator Rollers I need.
2) Which Belt.
3) Which Oil pump Belt.
4) Which size of carburetor Needle I need.

Grateful for any advice, help and suggestions offered.
Andrew