So this probably goes against most conventional wisdom, might violate warranties/agreements, or could cause the world to implode, but here goes.

I want to rip my kid's DVDs that I legally own and import them into the 6412. There are obvious space limitations and guide issues, but instead of trying to get video off, can I put it on instead? Cheers.

You cannot.

The TivoHD is the only DVR that allows you to do that, and that feature (TivoToComeBack) won't be supported until a software update in November.