What size? I assume its either the OA/ OB/ OC?
Not having autothreading isn't terrible for toolroom type work. If you are around to keep an eye on it I really like them for the simplicity. You won't have much luck running night burns though.
As for the machine itself, If its one of the old 0 series, they are worth maybe 4-5k. This is coming directly from methods, If I remember correctly they wont even take them on trade in anymore.
The biggest problem with those old fanucs is they did not come equipped with glass scales like the new machines, so doing tight tolerance work is can be problematic, especially if you have to make a part that fits precisely with somebody else wire work (a punch that fits a retainer somebody else burned for example). The bigger the work piece, the more pronounced of a problem this could be.
Another word of caution, the part support for machines through methods is something like 20-25 years, so if you have a problem, you are on your own to find parts.
Edit:
Also note, depending on how much its been run, you could expect to need to sink another couple thousand into guides and contacts right off the bat. If the guides are bad, its an incredible pain to rethread the wire by hand.