upgrade PostgreSQL 8.x on production FreeBSD

Could anybody point to an on-line resource about the steps involved with
upgrading of PostgreSQL 8.x on a production FreeBSD 5.4 with minimum
downtime (i.e. 1 - stop db so that no changes happen 2 - dump 3 -
upgrade (ports) 4 - import 5- start db).

Thanks,
Iv Ray