A conundrum for those more mechanically inclined than I am...I have an '03 6 4 cyl.w/67k miles (only owner). I went to pull into traffic and all the getup disappeared, so I immediately pulled into a parking lot and noticed the battery light was on and the car was stuck in 3rd gear; never shifts up or down. I was late for work, so I stole my wife's car and when I came home that night the battery was completely dead. I got a new one last night. It now starts up fine and goes straight into 3rd gear when put in drive and the battery light is on. I'm guessing that a diagnostic will tell me the alternator is dead, but I'm worried there are computer issues. Could the alternator issue be causing this? Is it a short? Or am I screwed on a computer issue? By the way, anyone know how to reset the computer?

Thanks in advance!