I don't have the answer but I do have a suggestion on VPN in general which may apply when you get further along. Make sure the IP address range at each end of your VPN tunnel is differnt. ie...Location one's range could be 10.11.200.x and location two could be 192.168.200.x but both could not be using the same range of address like....10.0.0.x.
If the ranges are the same on each end you will not be able to browse for computers or servers via IP address or much of anything else either. Having the same IP address range on each end results in a lot of netowrk confustion. The VPN thinks you have a huge network with conflicting address and seems to just shut down all browsing.
Just a thought..
Using Mac OS X Server to make a site-to-site link was theoretically possible with Mac OS X 10.6 Server. It was done via a command-line option called s2svpnadmin
See http://webcache.googleusercontent.com/search?q=cache:5eH5QIThXLYJ:docs.info.appl e.com/article.html%3Fpath%3DServerAdmin/10.6/en/ns212fab54.html+mac+os+x+server+ vpn+site+to+site&cd=1&hl=en&ct=clnk&gl=uk&client=safari
Note: Apple seem to have removed a lot of old (even Lion) documents from their site so I am posting a Google cache URL above, however even the Google Cache will loose it soon.
You could in Lion or Mountain Lion Server run the following command to see if the s2svpnadmin utility is still available
Unfortunately Apple have been dumbing down their server software so that while it is becoming simpler to setup it is also becoming far less capable.
Personally, I would consider using a hardware device for doing site-to-site VPN links. Most business class Firewalls have VPN capabilities to do this. Most consumer level routes/firewalls do not.