Try www.kbb.com and use the "private owner" sale to establish a fair price.
Then go out and look at other cars.  Be prepared to present a repair history
to a prospective buyer if you're looking to get top-dollar.  The body and
interior will be reponsible for holding the most value, IMHO, as long as
there aren't major mechanicals waiting to go south.  Also, having all of the
electrical gizmos in operable condition helps the value.

Chris
90 & 94 GXE's

why not keep it. it costs almost nothing now to operate it. i have an
excellent 91 maxima, too. i tried to sell it early this year as it passed
200,000 mark but did not like any offers. I end up keeping it, again. i
traded off 95 camry and 00 accord. maxima wins on our keep list. it has
excellent engine and transmission. I still get 22 local 29 highway and
emission test results are excellent. its pickup feeling even beats my wife's
new rx330. only thing i complain is no cup holder. do not throw away a
treasure unless you absolute have to.