I have a webserver in my local network. I want to make it expose to the Internet probably by port forwarding in my dsl router.

I wanna run it on https (secure http). If I make it listen to port 443, would it means all transactions would be encrypted? Is there a need to modify pages on the webserver or is it enough that it was running in https without editing the webpages?

This webserver has some accounting and I don't want to compromise the machine. If worry if somebody might sniff to the transaction.