"I really can't recommend that. Can't it wait until you're better? Do you really want to take that risk?" It's true that as far as they know, the world doesn't fully understand death yet -- but that might have changed, could change at any time. Sam does, however, have another option:

"You might not be a Pokemon, but I think you're similar enough to a few I'm familiar with that I might be able to help. Your lungs should be around the same place, anyway." He gestures toward the vague area of Bowser's chest. "I could give you an examination, even surgery if we both decide it's the right thing to do."

He really hopes it doesn't come to resorting to surgery, though. They just don't have the supplies to make it safe. Like anesthetics.