Not too far, and not too difficult.
If you have a road bike, you'll want to stick to the loop road and Route 3 -- I would guess it's a bit shy of 1.5 down the Gale River loop road to Route 3, then 3 - 4 miles down Route 3 to Haystack Road, then about 2.5 miles on Haystack Rd. Haystack Rd is a bit of a grind on the way in, but not difficult by any means. Maybe 7-8 miles?
If you have a mountain bike, you can avoid Route 3 and take the snowmobile trail, which will probably cut a few miles off the trip, if not even a bit more.
