I'd certainly recommend doing a security review of what exactly you're trying to do, and making sure you're not going to expose things to the Net you don't mean to. For instance, make sure you're accessing your code over a secure link, and not just sending everything in cleartext.
But that said, I wouldn't worry about DNS yet - you need to make your server accessible from the internet (probably a routing/firewalling adjustment). Once that's done, you should be able to access SVN just using the IP (assuming you have svnserv set up).
If that's working properly, you can assign that IP to any DNS name you control - usually that will be done on the DNS server, either yours or your ISP's/hosting company.
/etc/resolv.conf is only used to change how the machine looks up DNS entries, but it has nothing to do with which DNS entries resolve to that machine.