the way I would do it (and I'm about to do about the same thing with my mac pro)
download carbon copy cloner
http://www.bombich.com/remove the current 1TB drive and replace with the new 1TB
format to mac OS extended journaled using disk utility
use carbon copy cloner to clone the 80GB drive to the new 1TB (do this with no apps open and do not move/delete files in the process)
shut down
replace the 80GB with current 1TB and boot up
you should be good to go
I wouldn't do anything with the 80GB for a while, just to be sure it copied everything and incase you have a problem with the hard drive, you can just throw the old one back in
hope this helps
Iggy