One approach that would work is to keep your manually created trunk/branches/tags directories in SVN. Check out the empty /trunk into a parallel directory on your local workstation (Let's say directory #2, with your local project as #1). Then copy your project + code from #1 into that /trunk directory and commit to SVN.
Then you can make a 3rd directory locally, and check-out your SVN copy and ensure it compiles/runs properly. If so you can delete the intermediate #1/#2 directories, or keep your initial project as a backup just incase (but it'll be non-versioned). Then continue to use directory #3 as your new SVN monitored workspace.
If I'm unsure how my changes will affect work that I don't want to lose, I try to take an approach like this so the least amount of harm is done to my code if something goes wrong (say with a SVN command/operation I'm unfamiliar with, etc).