Send them to Sover Wong, he is an expert repairer and serviced several of my lenses and 3 cameras perfectly. He is in the UK so postage may add to the cost. His website has pricing on it for cameras here
. I did not see lens repair costs but they maybe there. he is responsive to email.
if you are handy with a screwdriver then youtube has several guides, mikeno62 is my go-to source
, here he is servicing the focus on a 35mm F2.8 - the steps will be similar for all Nikkors.