On my FZS600 2001 model I have checked them at 24k and around 48k as suggested but always been in spec.
Others may have clocked up enough miles on the FZ8 to give some idea if they are likely to have altered at that sort of mileage, but it's one of those things where for piece of mind I'd rather check anyway. Checking them on the FZS600 is not difficult but a bit fiddly with not much scope for doing any harm unless you are real careless. The manual or others on here will give you a good idea if yours is the same. The more difficult bit comes if they do need altering and I imagine the quote you got is allowing for that, although still seems a tad dear. Might be as well to ask them, and then it's up to you what you decide to do. What facilities you have, like working indoors at this time of year, and how confident you feel will decide it for you I imagine.
Good luck with it.