Not sure where you are located.
Here in Baltimore there is a company that sells used equipment called " Service Photo ".
As far as 'refurbished' lenses, I am not sure if Nikon sell refurbs.
I am a Canon user and if a lens has a problem we have it sent back for a fee they fix it and go over it, not sure if that could be considered a refurb so much as just a repaired unit.
Look in your area for a photography supply store.
The good ones cater to professionals, and may also affiliate themselves with schools in the area giving discounts to students for class materials.
I shop at Service Photo, I know at times I pay more there than I have to, but the service I get is well worth that added cost.
Another HUGE advantage to buying locally - you can walk in, test the lens before you buy it. If you mail order used lenses and there is a problem the hassle of returning via mail is a headache.