Using the /var/lib/pgsql/data directory in the absense of a backup for recovery

Hello all

I am a newbie PostgreSQL DB admin.  I have the following problem:
1. I have a redhat 8 box which has postgres installed.
2. I have reinstalled postgresql 7.2.1-5 (native postgres installation on
RedHat 7.3) on the redhat 8.0
3. I don't have the database backups from my 7.3 installation - I however
have access to the /var/lib/pgsql/data directory.

My question is... can I use this to recover the database from the 7.3
version.  We got hacked and the earlier system was unusable.

I tired to do an initdb but it would not let me provide the existing data
directory and got the following:

-bash-2.05b$ initdb
The files belonging to this database system will be owned by "postgres".
This use must also own the server process.

initdb: The directory /var/lib/pgsql/data exists but is not empty.
If you want to create a new database system, either remove or empty the
directory /var/lib/pgsql/data or run initdb with an argument other than
/var/lib/pgsql/data.

I tried to do fire up the postmaster process and could not fire up the DB.
I don't get a message the system just returns to the prompt without starting
the database.

Any help would be welcome!!

Thanks

Srinivas