Deviated-Septum surgery for a singer?

It should not grossly effect your tone or resonance. What happens is that the nasal area will become less of a problem and you may find it easier to create the tone and resonance you want.

I speak from experience: BA in Voice, with deviated septum....

If you can, try and enlist all the help you can get from a coordinated team of a speech therapist + your singing coach/teacher. Once the surgery has healed ( and please take good time to let it heal) you will want to proceed carefully to gently get to know your new capabilities. ( do you remember your first singing lessons? You had to learn things one by one until they made sense. You're going to consciously re-live that phase of your life, doing things one at a time to compare the before-and-after sensations)

You'll most likely feel more and different sensations of resonation in and around your forehead. Take the time, record yourself and listen critically, using the technique that has served you up till now, and find the changes that you will need to make. Your teacher and speech therapist can lend not only their moral support, but also technical details that may evade your attention the first time around.

You may have an easier time with gauging your passagio into your upper register after surgery, but since I don't know what limitations ( if any) that you have encountered, it would be hard to say what awaits.

my husband, a French horn player, had similar surgery done. I benefit because he no longers snores, and he benefits because he has an easier time breathing through his nose. can't say it makes a difference on his instrument though....

Ask your doctor if there have been any studies done on singers specifically.

Best wishes for a speedy recovery and an uninterupted singin gcareer.