We stopped "cutting it open to see what's inside" over a hundred years ago. Now we do it in a controlled way. They wouldn't just come here and start cutting us up. They'd observe, and then when someone dies of natural causes, cut that person up and see what's inside. And given that we are intelligent*, they'd be better served to try to communicate first.
*A lot of theories are that they wouldn't view us as intelligent. But I find that to be a load of bunk. We have artificial satellites. We have communications. It is clearly not natural, and a clear indication of intelligent life. They may be so advanced as to view us as useless in terms of new scientific insight, they would treat us as an intelligence, albeit an inferior one.