If you decide to go for it yourself you need a decent bone blank. Most guitar shops have them in stock, and if not can order them quickly. You can also get them from places like AxesRus online. Brass was very fashionable in the mid 70's and made it's way onto late 70's/early 80's production instruments. It was thought to have good sustain due to it's density, but it does damp high frequencies a little due to being so soft.
Basically, it's a generic Fender replacement. The only issue is whether or not the nut slot has a flat bottom or a radiused one. I've done replacements for Stingrays in the dim and distant past but can't for the life of me remember which version Musicman use So unless anyone can say for sure, you need to remove the old nut to find out. However, if in doubt, a flat bottom replacement nut is easy enough to shape to a round bottom. I mention the method in the thread...
You remove this style nut by gently tapping against the side of the nut with a hammer and drift. It's always a little nerve-wracking
Where you have a lacquered neck you need a very sharp blade like a scalpel or modelling knife to careful cut through the lacquer around the nut. Done cleanly it's near invisible, but if you need to do a little touch-up work to the lacquer you will find Superglue to be an excellent candidate. Apply with a cocktail stick/pin along the repair, leave to dry over night, and carefully sand back flush. Go for several applications rather than one big one.
A friend of mine is a brass instrument repairer with a workshop in Glastonbury, and he's always being asked about guitar repairs. And so far he hasn't found anyone there to refer people to.
When the going gets weird, the Weird turn Pro.