Well, this sounds like you're connecting in Auckland all ready. Maybe this is the time to splurge on Qantas or United business straight to LAX or SFO. Then maybe take UA or AA in first to MCO. Also, get rid of the lay over if possible. If this is one of your first few times in the US and after surgery to boot, maybe it's better to eliminate the confusion. Another option would be to stay a night in LA for a day or two so you don't over strain yourself. If you have to take this trip, this is the time to empty the piggy bank to ensure comfort.