This is the link to the Italian White Pages:
As you can see there are more than 500 people with that surname in Sardinia.
Also "Guestino" is not a correct first name, may be it was Guerrino or Gesuino. The name Benigna is correct as an Italian first name.
I doubt that the parents of a person born in 1934 are still alive as this means that their birth year would have been 1910-1915 and makes them very close to 100 years. But you never know, Sardinian people are famous for their longevity so good luck.