Upgrading from 7.4 to 8.2

Hi!
I have PostgreSQL 7.4 DBM and want to upgrade to 8.2 (latest in version 8 I quess).

Can use the DATADIR from 7.4 and just upgrade the DBM/postgresql server to 8.2?

Is the upgrade from 7 to 8 procedure written down somewhere? (could not find anyting at
http://www.postgresql.org/docs/techdocs.2,except from 6 to 7) 

I guess I could dump all my data and restore it later but it would be much nicer if it was possible to just start a new
PostgreSQLserver with the old DATADIR repository! 

Thanks!

/Rick

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