I had to give a RTB injections a few years ago (and I am a nurse, so I do it all the time anyway). You do not need to go super deep, just enough to get into the spot he showed you. You should not be close enough to the spine to be an issue. The other thing is you either need to hold the snake secure yourself, or have someone else hold it, in case it moves when you place the needle. I really is not hard and if the vet was concerned you would hurt the snake, they would not send you home with the stuff to do it.