Hello!
That's a real nice looking bike there. I don't know about your area,but where I am (Virginia) that would be about a $2200 bike. Only because it appears to have a rattle can paint job. If it had/has proper paint it would easily be a $3,000 bike.
Fork seals are easy to do and don't require any special tools. You can have them changed out in an hour or two if you've never done them before. Not a bad job at all.
I don't see any redflags myself. The ad claims all original,but that exhaust is aftermarket. No big deal,it's probably better than what came on the bike anyway. The tires look to be a pretty old style of tread pattern. Look up how to read date codes and tires and make sure they are not real old tires. Any tires over about 4 or 5 years old you really probably shouldn't be riding on them,so consider that when you are haggling over price.
Overall, I think its a great looking bike. I'd like to have it myself
Good luck with it!