The first thing for you to do is to re-tension the spokes yourself using the current existing spokes. Do that before you start replacing stuff. I suggest you read the below, close Bike Forums and call it a day. I wouldn't bother paying a shop to work on the wheel for you. It's a simple job that you can learn in no time.
https://www.sheldonbrown.com/wheelbuild.html
I second this advice. Another good (and affordable) source of information which I've used for several years is Roger Musson's
Wheelbuilding Book.
I sort of got "arm-twisted" into starting to build my own wheels (story, briefly,
HERE), but have never regretted it.