-You have to go buy the pump, maybe some other tubing/hose in case you have to siphon.
-You need to have or acquire 10+ gallons of hopefully correct gasoline containment
-The junkyard has to let you in to do this. If you show up w/the above gear they're going to ask you what you're up to and will likely kibosh the idea of violent metal-on-metal contact to puncture a tank of flammable liquid.
-Of course this doesn't account for the likelihood that the gas hasn't been drained by the yard for safety and/or to fuel their rigs....which is likely has.
-If the wheels (or even 2) are salvageable from the car, they're gone and the car is now resting on it's belly. Good luck accessing a drain.
-If the damage is a total, but the car has decent salvage parts value, it'll be held in the junkyard-first-crack-at-it area to pull airbags, ECU, interior bits, battery, etc. Insurance won't allow someone into that area.
It's a minor victory in the face of losing the whole car, but there is a hugely diminished value attempting to chase down the gas.