Several problems with installation on FreeBSD - how to reinstall without loosing data

Even though I have had PostgreSQL for years, I think I am in fact a true novice. :-)

I have installed postgresql-server-9.2.4 on FreeBSD 9.1-Release.

A couple of month ago, I had a break-down of my server and since then, I have had problems with a lot of things. But at least I can see that pgsql is not configured correctly.

First, it started to complain about the role "root" did not exist. I don't think I have created anything that should refer to "root". Even though it's a potentially dangerous thing to do, I created the role. After that, the error message was that the "root" database did not exist. So I just created an empty database called "root". Then the server complained about loosing connection to a client.

I think that the best solution would be to reinstall pgsql. But it would be very inconvenient to loose at least one of the databases (I use it as part of at calendar server). Can I reinstall following a tutorial like this one and get the vital databases back?