Valium AND Laughing Gas?

I have very very high anxieties or anxiety attacks when going to the dentist. TomTomorrowam going to get some cavities filled and to make the process easier my dentist has prescribed one tablet(5mg) (I'm little only 4'9" and 87 pounds) of valium and hour before I go, and during the procedure I will have the laughing gas and novocaine. If anyone else has had both the valium and the laughing gas, can you tell me how it went for you or what to expect? Thanks.