transmission problems

I have a 98 with a 2.2, 3spd, and 99k miles. I recently slid into a curb twice when it was slippery out. Since then the car has been making a humming noise while going down the road, it is worse on deceleration. While on a lift, the transmission has grinding noises in drive but not in reverse. There is no difference in the alignment of the car, just a small vibration, but not from the steering wheel. Also, does anyone know if a 3spd transmission from a 1990 Olds Calais will fit in my car. Both Transmissions look the same and have the same pan bolt patterns.

Sound more like a wheel bearing to me...

I forgot to mention the transmission fluid level is very low and will not rise no matter how much fluid I add, it just goes back down, and there are no visible leaks.