I've alway used respected local repair shops, Detroit, Orlando, Chicago, but it's been quite a few years, so I don't know who is still in business, and my repairs have all been Canon, Olympus and Leitz, the Leicas going to factory for rebuild.
Lens repair is usually flat-rated for disassmbly, cleaning, lube, minor repair. Maybe under $100 to service a zoom, to several hundred dollars depending on complexity of optics and movements, andnthings like internal motors and weather sealing.
Nikon has a list of authorized repair stations, but for your zoom, they may want to do the work themselves.
Your problem is likely repairable, probably a tab out of a slot in the zoom mechanism, but you have to figure out what the lens is worth to you, weigh the repair costs vs replacement. The low prices of some of today's kit lenses sometimes make repairs of more expensive pieces questionable, it not really a high value lens.