BE58 pilot reported they experienced a CFTT event while troubleshooting avionics in turbulent flight conditions. Pilot returned to departure airport and landed safely.

Narrative

Upon leaving crosswind on takeoff experienced continuous moderate turbulence with up and down drafts. I also attempted to adjust the brightness of autopilot display and G500 displays and Garmin GTN 750 Xi; and somehow in the process of doing this task I got both of the nav/display units to go dark. Meanwhile; I lost GPS input to the G500 [for heading] and thus lost the autopilot. It is not unusual to lose GPS input for a few miles in that area. It was quite dark out and I attempted to regain use of the nav/attitude units by recycling them; and I got slightly behind the aircraft leading me to descend to about 1000 feet AGL; give or take; I am not sure exactly how low I went as I was not only dealing with the turbulence but attempting to re-establish use of my instruments. During this time; I advised Tower of my situation and announced I was returning to the airport to land. I was probably three or four miles away; and Tower turned up the runway lights to assist me finding the airport. I ended up reaching the west end [departure end] of the airport inadvertently and Tower instructed me to enter a downwind to reach the approach end of the runway. I landed; taxied to hangar; shut down the plane and then turned the master switch back on to check the avionics. Upon powering up the instruments and avionics; all worked normally. Therefore; the results of my dealing with several issues as described above are that I descended more than I should have and became disoriented as to the exact location of the runways.