I wouldn’t re plate it.
That costs money and I don’t think it will add enough to the value to re coup the cost of the plating.
Let the new owner decide to do that, if they wish. They will appreciate, that you let them decide, and oversee that fate.
The stem is a hard to find part, but so is the speedometer/housing and the control buttons.
Without those parts, it’s a step closer, but still a long way from nirvana.
My guess is, that you could throw it out there for about $1,000, maybe $1,500 and see if you get any bites.
But, again, without those critical components, it’s just a hull.
Better than nothing I suppose, but if you’re going to spend a thousand, it’s probably worth waiting for a complete kit, which could probably be had for about the same or slightly more coin.
That’s about what the hierarchy of rare stems seems to be going at the moment.
Just my opinion, for whatever it’s worth.