Problems 03 MCarlo LS

I bought my Car (2003 Monte Carlo LS) brand new less than 5 miles on it and after about a year I noticed when I would slow down like at a stop sign or so the lights would dim and rpm's would drop drastically close to 0. It normally idles between 1/2 and 1 rpm. but it drops. I took it to the shop because also when I would switch my air conditioner from like defrost to top vents or any other direction it would stick and not change.

When I took it to the dealership they said that it was electronically controlled and sometimes it take longer to change. No recalls had been issued about the lights dimmed but they have had the same reports from other MC owners. because a recall had not been issued they couldnt replace any parts or fix the problems.

Now my warranty is expired and my air conditioner is stuck blowing in defrost ground and top vents. My lights are still dimming when I slow down.....

WHat should I do?