Being a 17 year oldie is relative. Run hours counts more than age. You guys like running very old dinosaurs well taken care of, this one won't be the exception, should not dissapoint. Being an actual model which has not been electrically nor mechanically upgraded a bit as actual one, will assure fresh available service parts and long live the outboard. .
Knowing was fully serviced I would buy it, ask for a price reduction and a written warranty for the service received for my peace of mind. A new 2 strokes 30A4 costs more than 4 K, turn that 25C3 to a 30A4 for peanuts cost, latter can maximize a less prop pitch if in need to bump wot revs towards max range in case it's needed..
Happy Boating