Q: shifting problems and the vehicle will not go backwards. Plus it will try to lunge forward in park.

Hi there. What could be the issue is the main valve to the transmission may have disconnected from the shifter lever on the side of the transmission. Raise up the vehicle and put it on four (4) jack stands. With the brakes pressed down, take the transmission shifter and put it all the way into low. Let off the brakes and see if the wheels turn. If they do, speed up the engine and see if the transmission shifts. If the transmission shifts gear once, then low gear works. If the transmission shifts more than once, then the gear selection is not in low. Stop the tires with the brakes and hold the brake down. Put the transmission shifter in reverse and let off the brake pedal. If the engine loads up but the transmission does not move, then there could be an issue with a cross leak inside the transmission. If the engine does not load up, then the main valve is not aligned up with the reverse application. Press on the brake pedal and slowly move the shifter up and down near the reverse selection. If the engine loads up, hold the shifter where it is and let off the brake. If the tires turn in reverse, then the main valve is out of alignment. If the tires move forward, then there is a cross leak inside the brain of the transmission (valve body). I recommend seeking out a professional, such as one from Your Mechanic, to help you diagnose your transmission issue.