I'm not sure which 1700 you have, but it should have at least 1 ethernet port built in. You can use this for your LAN interface. If you have 2 ethernet ports, you can use one for your LAN and one for your WAN. If you only have one ethernet port, then one of the 4-port switch WICs will do the job.
The 1700 series can terminate VPN connections assuming you have the proper IOS and feature set.
Hope this helps. If so, please rate the post.
Brandon