So you dropped the pan and changed filter... did you get the right filter for your pan. Some come with shallow or deep pans where there is a filter specifically for both. Also, the shift cable is right there next to the transmission bolt, double check and see if it was harmed.
Also, when you added fluids back to the tranny, how many quarts did you put in? I could never read the fluid level on the dipstick, I think mine has been over filled for over 50K miles. I think if you drop the pan and change filter, you're suppose to put 5-6 quarts back in.
Oh yeah, there was a cork gasket that came with the filter, did you change out the old and put in the new OR left the old in there and stuck the filter in OR did you leave the old and also put the new...
I'm just asking all these questions since it will help us help you.