Yes foward 3389 to the LAN ip of the computer you want to access, then when ur outside the lan you type in your wan IP and it will foward the request to the computer you specified. then once ur in you can rdp to other comps on the lan.
With all due respect John, I am the head of IT and I have it on good authority. If you type "Google" into Google, you can break the Internet. So please, no one try it, even for a joke.........It's not a laughing matter. You can break the Internet.