2006 Chevy Vivant Stalling and Sluggish engin

I am not sure if this is a front wheel drive. (I don't have a manual.) I just purchased this car and it is having an inimittent problem. When I get to an incline, if I stop, when I press the gas again, the car doesn't seem to want to go ahead, (like a "stall") then when I put it in reverse, the gear "jumps" into it (with a sound.) The engin light also comes on. Then as I am driving after this, the car seems to want to stall (or go in a lowerr gear) when I press the gas. (I woulld have the car in DRIVE.) After I stop and take the key out (once or twice, ) the car seems to return to normal, and the engin light goes out. What can be causeing this and is it an expensive repair?