I would fix the obvious first. If the spedometer isnt working either test of replace the VSS. If the key is on and you spin the VSS while its plugged in it will produce a signal, if the spedometer doesnt read anything you could always try replacing the sensor.... VSS is a input to the pcm to determine shift points, I mean is that not an obvious input for the pcm to determine shift points by how fast the vehicle is travelling as well as TPS to determine load.
Fix the spedometer, check your transmission fluid with the vehicle running... If its brown and smells burnt then you may have something serious going on int here. You may also have a leak and thats why your transmission isnt responding properly due to low oil in the valvebody. If that be the case the damage has been done.