IMHO it's best to do the 685 at a private tech day. Too much going on and too many people want to fondle the parts. With the detail work required, best to do it one bike at a time for the average person, with just a few people there.
Figure a little over $400 including shipping and cylinder work.
About $255 including shipping for the 685 kit, $100 including shipping for cylinder boring & honing, ring fitting, etc. Head gasket, cylinder to headpipe gasket, and cam chain tensioner gasket. Oil filter, oil, coolant.
all the best,