Help with crazy display

Have a 2004, stage 3, 140K miles, all original, oil change every 3K, 2 sets of Michelin Hydro Edge tires, 1 new set of front brake pads. Never a problem until mile 135K when crossing Hoover Dam. Radio quit, then got "Trouble with A/C connection" when I tried to get to the Climate screen to turn off the A/C. A/C was working fine! Tried to get the Info screen up, and nothing happened for a few minutes, finally got the Energy scre a repeat of the en up, but nothing was working.
Made it home to St George, UT without any problems, except the displays took seconds to come up. Parked over night, then next morning car would not start. No sounds, no lights. Zippo. I had read about the 12v battery, and I replaced it with no trouble 4 days later, and all seemed fine. Everything was working fine.
Then last week drove to Tucson, 500 miles. Had my Garmin on the entire trip. Returned to St George 2 days later, and I had the same problem again. This time, the radio quit by itself. Came right back on when I pushed the radio power button. Very slow displays, on the energy display the wheels turn, but no power flow lines. No display when I change temperature or radio volume.
Other than this, the car seems to drive fine except for the radio shutting off by itself. Any one have any ideas, before I get stuck 200 miles from nowhere?

Thanks!