I'm so sorry, KT. Many chin-scritches for Byron.
edit: read only after you've had your away time! (not scary, just... for later) I know you probably don't want to think about it much just now, but when you're ready to, I've known amputee cats who've gotten around like absolute demons for years afterwards. It's a rough thing to even think about, but if it's what the surgeon says, he's got a good shot.