Most Fender maple necks are finished in Polyurethane. Older Fenders (CBS) are polyester. The vintage and custom shop versions are Nitrocellulous lacquer.

If I were doing it, I would use Nitrocellulous Lacquer for the back of the neck and the headstock. I'd oil the fretboard (that's what I like). For re-sale, I'd do the whole neck in nitrocellulous lacquer.