I've owned a couple of Archers and a Dakota. Fine aircraft. How long a 100hrly will take depends on the plane and who's doing it. My 100hrlys varied between $1500 and $11,000. Inspection part should not be more than 14 hours - but costs will vary according to what they find peeping into those little holes with their torches and mirrors on sticks. Then if they decide to take the tanks out (the only way to see parts of the spar) or drop a wing off for a wingwalk or something.. start taking the proverbial sharp intake of breath and thinking extra days not hours.
One thing I have found is that 100hrlys on a PA28 are almost always a bit less than on a Cessna....