The pilot in the retractable landing gear-equipped airplane reported that, during the cross-country flight, the autopilot failed, and he struggled to use the sectional charts. He added that heat and wind made the flight uncomfortable, and smoke from wildland fires decreased visibility to about 5 statute miles, so he decided to land. He completed some of the GUMPS (gas [proper tank selected], undercarriage [gear down], mixture [full mix for landing], and propeller [high rpm setting]) checklist and decided not to extend the landing gear to have better control. Upon arrival at the airport, he decided to leave the landing gear retracted as he searched for the windsock on the airport, but he could not find it. Subsequently, he attempted to contact the airport on the Unicom frequency, but he later determined that he had used an incorrect frequency. He decided to land on runway 5, which he later identified was the incorrect runway given the wind direction. He forgot to extend the landing gear before landing. The airplane sustained substantial damage to the longerons and bulkheads. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.