Hello,
Yes, you can use this router for Lan to Lan (site to site) and remote access (vpn clients), the requirement is version of IOS 12.2.8T and later, Cisco VPN Client 3.x and later. This is a sample configuration for your scenario:
http://www.cisco.com/warp/public/471/ipsecrouter_vpn.html
If you have a Smartnet contract, you are able to donwload the client for Free.
Regards
Arthur