Use PPTP as suggested, or search for the PuTTY Howto that tells how to configure exactly this scenario to manage an SME server.
If server managment is all you want, the SSH (PuTTY) solution is probably better and more secure. The advantage of PPTP is that once connected, you can do anything on the remote LAN just as if you were there, so if you think you'll want file sharing and such, that's the easier route. (Especially if anything you'll want to talk to on the other end is dynamically addressed - for instance using SSH to make VNC connections to remote DHCP-addressed PCs can be maddening, so PPTP is much easier there.) I use both, but keep PPTP locked down pretty tight. If you enable SSH, you can always use that to bootstrap yourself up by then enabling PPTP if you really need it, so it's off until then.
HTH,
Dub