Rather than IPSec VPN, why not use svn+ssh? I only mention this because ssh-ing to an IP is a helluva lot more simple than setting up VPN access - just advertise a random port for your servers, forwarded to your internal server.
You will not screw up your server by adding a single route to a 10.x.x.x network (such as 10.1.1.0/24.) Internet-bound traffic will always go to your default route anyway.
Sorry I can't provide a soup-to-nuts script, but try setting up ssh keys and using svn+ssh - much simpler, and no need to change distros or anything drastic like that. :)
Edit: If the source is anything to do with work, then in my opinion your IT department have a duty to make this as simple as possible whilst maintaining security. What is the VPN server? Setting up a temporary connection should be pretty simple but I need to know more about the type of VPN you use. Is it PPTP?
There's no such thing as an IPSec firewall. In my experience there are just general purpose packet filters, commonly referred to as firewalls. Generally speaking you just use a firewall to allow arbitrary ports, with a default deny rule for anything else. It's very simple to expose a port for this, it's just a matter of process.
Also, the fact that the server runs Windows doesn't mean it's not running svnserve. How do you access the repo? What is the protocol at the start of the URI? svn://, http://, etc.
Given that you can connect by IP address, the problem is one of name resolution and is likely to be a NETBIOS/DNS issue
At work, your machines are probably on a domain such as "company.local" so when you connect to, say a machine called WORKSTATION its FQDN (Fully Qualified Domain Name) is actually WORKSTATION.company.local
At work you will likely have a fully operational DNS/WINS/NETBIOS system up and running so both the short and long versions work
At home, I suspect that the VPN is not picking up the correct name servers.
If you try connecting to e.g. WORKSTATION.company.local i.e the long name, does it work? If so then its a WINS/NETBIOS problem but if not it is a DNS issue
Best Answer
WinRM (remote management). It looks like it takes more then a few steps to get it working securely over the Internet using HTTPS but it's designed for HTTP remote management and I've watched videos and read much on the topic of WinRM + PowerShell, etc. I just haven't used it remotely through firewall yet.
http://msdn.microsoft.com/en-us/library/aa384372(v=vs.85).aspx
updated versions of WinRM and PowerShell for 2008
http://www.microsoft.com/downloads/en/details.aspx?FamilyId=d37e25cf-db05-4b23-a852-cdf865d81b82&displaylang=en
How-to
http://blogs.msdn.com/b/powershell/archive/2009/04/10/configuring-powershell-for-remoting-part-2-fan-in.aspx
http://thepowershellguy.com/blogs/posh/archive/2007/07/24/powershell-using-windows-remote-management-with-alternate-credentials-to-retrieve-services.aspx