safest way to upgrade a production server

[John Almberg]

I'm a newbie admin, responsible for a half-dozen of freebsd servers,  
most of them production servers.

We switched from Linux to Freebsd at the beginning of this year, so  
all of these servers were newly installed in Dec or Jan. I know I  
*should* be upgrading them, but so far I haven't had the nerve.  
However, I've been working with Freebsd for 8 months or so, and I  
feel ready to take the plunge, if necessary.

So, my first question is, do I really need to do this?

If so, what is the minimum amount of upgrading I can do to be safe?   
And how?

I've studied the Upgrading chapter in Absolute FreeBSD, and think  
what I need to do is patch the systems to the proper errata branch.

I also think I need to do this using freebsd-update to do a binary  
update, to upgrade on an errata branch.

Am I on the right track, here?

I've never done this, so will try upgrading a test system, first. If  
all goes well, I will give it a whirl on one of the production servers.

Frankly, I find this idea terrifying, but I guess it needs to be done.

Here is what we are running...

 > uname -a
FreeBSD ***servername*** 6.3-PRERELEASE FreeBSD 6.3-PRERELEASE #1:  
Mon Dec  3 09:46:53 EST 2007     root@***servername***:/usr/obj/usr/ 
src/sys/INET_ON  amd64

Any hints here, much appreciated!

-- John