Immediate surgery for my dog

Brought my boxer to the ER this weekend he wasn't waking up on his own Saturday morning, took him in for tests and they found a mass on his spleen, with his heart condition it's a risky surgery, his condition wil get worse with out it though, they won't know if it's benign, til after its removed, have to have consultant done with cardiologist because of his heart condition also, his surgery is thursday July 13th.