"But would be a $80-150 option, for what should be a no-cost warranty claim"
Did you tell them it was for warranty work? It seems to me, they should make good on a warranty claim. Perhaps there's an authorized Seagull repair center nearby that might have some more clout.
But, I doubt you'd regret replacing them.
By the way, StewMac has a set of Gotoh tuners on closeout for $30
https://www.stewmac.com/Hardware_and...d3_Tuners.html