Postgres is very easy to maintain. I just keep the dabatases backed up and swicth to the newer versions a little after they are out.
psql is your friend (PG's equivalent of sql*plus). If you are doing multiple boxes or external clients, look at the permissions system (pg_hba.conf). If you are not doing that, then don't have PG listening on an IP port (defaults to 5432).
Run VACUUM ANALYZE every night.
By default PG comes compiled with an 8 Kb block size but you can recompile it for 16. Instructions for that, plus command line options to increase your performance plus a script that Don wrote that a) backs up your AOLserver DB, b) gzips and ftp it to a remote place and c) runs VACUUM ANALYZE for you, are all in the docs at www.openacs.org/doc/openacs (Simple PG install Guide and Getting Started Guide).
That's what I can think of right now. Do you have any specific questions?
