So I've never taken a coil shock apart but if it's leaking oil doesn't that mean that mean it's the shaft seal that needs replacing, not the piston head?
From what I've gathered, there is a "head seal" which is an aluminum knob with and outer 40 mm seal and inner 14 mm bladder-looking seals. A new one is around $80. Then there's a rebuild with $40 of seals only, but you have to know what you're doing. Overall, it's not rocket science, and there are YouTubes showing the procedure, but you do need to discharge it carefully and refill it up with 250 psi nitrogen afterward.
I took my bike to a Zero dealer. It turns out Zero does not sell seal kits, only the entire shock. And that's "shocking" because it's a pretty generic SHOWA 40 mm x 14 mm. I've been told by a mechanic friend that a 40x14 head seal is standard and easy to get.
So the dealer still has it currently, and they are ordering parts from Race Tech. It *might* be done Tuesday for $180 + parts. I should have just taken it to a local shock specialist because we have good people here.
Since I already got a new FXE, I'm just fixing the FX to sell it. The dealer is also a consignment seller, but after I described the weak battery situation, they won't take it. I can't blame them. It'll be a Craigslist deal. Someone will get years of use out of it, but only for a commute under ~30 miles.