Unless the front sight is far out of alignment with the center of the slide, I would start with the rear sight first, it may be all you need to do. I would start with the rear first.
Adjustment is covered on Page 34 of the manual for both windage and elevation.
https://ruger-docs.s3.amazonaws.com/_manuals/srSeries.pdf
The front sight can be drifted/moved. Unless you and/or your husband feels really comfortable with your skills, I would recommend taking the gun to a gunsmith to move the front sight with a "sight pusher" so you don't mar the finish or come away unhappy. It won't cost much. My local dealer/gunshop/gunsmith who I bought the gun from actually did mine for free in about 5 minutes (nice guy) - it was offcenter by about 1/32nd of an inch from the factory. He pushed mine back to perfect center and then I did all my other adjustment and sighting in with the rear sight procedure. That's what the factory would recommend, I gather, since they don't talk about moving the front sight.
But yes, if you feel up to the job you can move the front sight yourself. Use your judgment and care. Use a soft drift, field strip the gun and clamp the slide firmly but use something between the jaws of the vise and the slide so you don't mar the finish of the slide. That's how I'd do it, anyway.
Update: There is a video that outlines moving the front sight of an SR9c on YouTube. The SR9 is the same for all intents and purposes. I didn't do mine myself, but I think the procedure is basically sound...as long as you're careful and not moving it too far. I don't know about using the wrench, I'd have chosen something else, but as long as you're careful (which this guy seems to be) you should be OK.
Here's the video. Go slow, don't hit yourself with the hammer, etc., etc.
Here's a picture of that page of the manual in case their PDF doesn't come through well.
