H4 to h1b change of status

Hi, My wife is on H4 visa recently her H1b got approved under consular processing, As she is already in US under H4 visa i would like to file Change of Status. While filing for COS do i need to submit I-129 as a new Applicant or Amendment or only I-539 is enough for Change of Status ? Can i also know the fee for change of status. thanks!!

Hi Would like to take your suggestions as Im in the same boat. Please help here