To be honest the price will not be cheap. We only sell our forks fully serviced with clean stanchions, new wipers, springs of your choices and a serviced damper. If you want to upgrade to Ti bolts we can do that as well.
I have to double check but I think the fork on the main page of our site is available if you want to see the condition. https://specialtyretroproducts.com/
400 is step. You can get a decent fsx for that.
But I understand the conditions of yours.
Last month a DH was sold for £70. Needed a refurb, but thats something I can do my self.