Laura, I'm so sorry to hear that Corkscrew is still at the vets and that he may have crystals. I sure hope that the procedure goes well tomorrow.
Cirrus was so blocked up in March that he had to have a catheter and then he went through the surgery to make him pee like a female. It also cost me more than the average cat because he's semi-feral and becomes very scared and vicious at the vets so they have to put him under to do simple procedures. Even though my vet knows this, he tried to give him his meds without putting him under and he bit him so he's now known as "killer" at my vets office.
Prayers and positive thoughts are being sent your way. Please take care and keep us updated when you can.