That would be correct. Once you finalize a DVD-R (not a DVD-RW) you cannot make any changes to that disk. It pretty much turns it into a readable DVD for normal DVD players. this makes it hard to work with, import and edit footage. My best suggestion for you is to plug your DVD camcorder (with the finalized DVD in it) via USB and connect it to your PC. Your DVD camcorder should come with a built-in VCR mode and you can import your footage that way. Other than that, that's all you can do.
Imagination and discipline are like yin and yang; both are completely different and yet without each other they are nothing.