Moving data to different hard drive /or/ incremental backup

I've been setting up a server system on a hard drive in a test box that I
think is close to ready to be moved to the main server (both are linux on
i386 machines in a small network of about 10 machines)

I'm having trouble finding instructions on how to handle my postgresql data

I've been using pg_dumpall to make backups and once I fed a backup file to
postgresql on the backup server

I can't get the test server to take the updated data that way (it seems my
problem is at least partly due to the fact that the structure of the tables
_and sequences_ have changed during development of some of the databases)

I'm a definite newbie at db admin - can someone point me to suitable
instructions and/or a concept of what I should do?

I've got a feeling that I should wipe the databases from the test server and
do a complete restore from a backup - is there a way to this this without
having to erase each database individually?