[mythtvnz] Upgrade Mythbuntu 7.10 to 8.04lts to get 0.21

[Noel & Di]

Hi all
I currently run Ubuntu 7.10 and want to get the new multi-rec capability 
of myth 0.21.  What is the simplest way to upgrade - (I have ceased my 
efforts trying to get myth to use a second HDD for expanded  storage, 
lack of knowledge and fruitless hours of perusing the forums has taken 
it's toll on the WAF).  Should I use Mythbuntu's package manager to 
upgrade - then how do I get 0.21 in there without losing all my 
previously recorded programs? 
Thanks
Noel,
an old DOS junkie who is slowly coming to grips with linux.