Upgrading from 8.0 to 8.1 on Debian

Hi All,
I am a bit stumped. So I have a couple of Postgresql versions on my
server, namely 8.0 and 8.1 (using Debian package manager). I am trying
to get 8.1 to be the default database and delete 8.0

I used pg_dump to dump my db's into a file (Question: Where do I dump
the data of the tables in the db?).

I tried running pg_upgradecluster as shown below, and I get an error.

jarraa(at)proximity:/etc/postgresql-common$ sudo pg_upgradecluster 8.0 main
Error: target cluster 8.1/main already exists

I went through /usr/share/doc/postgresql-common/architecture.html and
am a little lost.

What would be the step by step process in this case? I would like to
backup the db (plus its data), then point everything to the new
Postgresql version and get all my db's on to that.

Any help would be much appreciated.
Thanks.
-assad