After completing a short cross-country flight, the pilot returned to the private airport where he based his Cessna 182Q. The airport was surrounded by terrain obstructions, and as a consequence, an operational restriction existed which requiring him to land to the north. After joining the traffic pattern to land in the required direction, he flew the downwind leg to the 2,000-foot long runway and "checked the windsock." He then turned on the base leg of the traffic pattern, approximately 1.5 miles from the runway threshold. The wing flaps were selected to the 20-degree position, and he turned on to the final leg. Approximately .8 mile from touchdown, the airplane encountered windshear and lost about 17 knots of indicated airspeed. The pilot applied "full power" and was able to re-stabilize the approach. The pilot reduced engine power once again and the "wind sheared to the tail" of the airplane just prior to touchdown, and the indicated airspeed increased approximately 15 knots. The airplane touched down "approximately 600 feet from the runway end," overran the runway, and the nose wheel dug into the "mud." The pilot then released the backpressure on the control wheel, and the airplane nosed over, damaging the propeller, both wings, the right wing strut, and the vertical stabilizer. The reported wind at a nearby airport, about the time of the accident, was from 200 degrees at 5 knots.