Hi Alan
From my reading of the Atmel site, the PU designation is just one of the ordering codes for the different models within 328P family. Check the table at the bottom of this page http://www.atmel.com/devices/ATMEGA328P.aspx
I think you should be okay since Arduino Duemilanove supported 328p.
So on the plus, what you have should work. As for Uno being more involved, I don't see that particularly. I presume from what you're saying you'll be using your existing Arduino Duemilanove as the ISP and using a breadboard or similar to drive the 328PU you're programming with the bootloader? These instructions http://arduino.cc/en/Tutorial/ArduinoToBreadboard should do the trick for you.
Cheers ! Geoff