Could you please tell me what you mean by "disk-level backup" ?
Just do a backup of your necessary data, make sure you have everything you need in a second location what ever kind, in case the update does fail. One way could be bit based image copy of your installation ...
Does the testing repo contain the packages of yavdr 0.4 with the new features like the channelpedia?
Like seahawk1986 did mention, channelpedia is not part of it and I don't think it will ever by part of this branch, rather it'll be reserved for the upcoming version 0.4 and further versions. There hasn't ever been the plan to provide a major upgrade for yaVDR 0.3 nor there is right now one. It just have been a offer for experienced users to get a newer VDR version on Ubuntu 10.04 (Lucid) on their own responsibility.
Are you running on a 32 bit architecture and is the resulting system that you could stable?
Well, yaVDR 0.3 has always been 32-bit installations. It's possible to use 64-bit packages from the Lucid repository, but this is a installation on your own manner.
regards
fnu