When your fluid is low enough, your gears will not shift. I experienced that before when I didn't put enough fluid when doing a drain/refill. However, as long as you don't change gears when it is low you'll be ok. In fact you can still safely change gears with no load since there's still residual oil on the gears. It's the computers stopping you because of low/no fluid.
If you can change your oil/brakes, you can at least drain from the bolt, change the two hoses and what looks like also a damaged coolant peacock and refill with fluid. Start the car, let it warm, check the level again while it is running. Then pull up the parking brake up, foot on the brake, put it in reverse see how it reacts. Do not move the car. If it seems ok, go to drive and repeat. Again, do not move the car. Depending on how it goes, it's your call whether to tow or drive to a mechanic.