Hi,

For most patients there are no perceptible changes in voice.  But Opera Singers are not most patients!  You have to be very careful with your decision as any slight changes in your voice may affect your career.  The nose is an important component of the vocal resonance system and although typically surgery of the septum, turbinates, & sinuses is more important in sound quality, even aesthetic rhinoplasty can result in some variation in voice. 

Generally, the less that is done during the surgery, the less risk to voice change but I would hesitate to undergo elective nasal surgery if even barely perceptible changes in my voice quality would affect my career.