Recently I had a scare with my 2006 Chevy Impala. I was in a parking space, still in drive, when the idle dipped low and the lights went very dim and I thought it was going to die. I didn't have any problems while in motion. I had the battery checked, and indeed, it was corroded. I had it replaced and had an oil change. But it seems that it still idles not so smoothly. It hasn't done the whole dieing thing again, but I am afraid that it will. It also seems to change between gears choppily. Theres not any noise or anything troublesome, just not smooth.
My vehicle is not under warranty and I am in college and can't afford a great deal and don't want to be ripped off at the mechanics, so any advice would be great!