1998 vt holden acclaim wagon auto problems

CAN SOMEBODY PLEASE HELP ME MY WAGON WAS RUNNING FINE THEN IT STARTED HAVING TROUBLE SHIFTING GEARS, IF I DRIVE NORMALLY WHILE THE REVS ARE UP IT WONT SHIFT GEARS AND STAYS IN FIRST, HOWEVER IF DECREASE MY REVS REALLY LOW IT SHIFTS UP GRADUALLY SOMEBODY TOLD ME IT MAY BE A SENSOR OR SOMETHING BUT IF I GOT TO A MECHANIC WITH NO IDEA AT ALL IM SURE HE WILL TELL ME i NEED A NEW AUTO ( BEING THAT IM FEMALE ) I REALLY LOVE MY CAR AND NEED HELP PLEASE ANY IDEAS ? MY TRACTION LIGHT ALSO CAME ON YESTERDAY.