Update messed everything...

Hi

I updated from 5.4-release to 6.0-current
Update went ok, but when I reboot after make installworld, ... total mess

First, i cannot even boot :
my nvidia graphics card made the system panicing
Fatal trap 12 : page fault while in kernel mode
Booting with the console line, I disabled nvidia.ko and the panic 
disappeared.
(for this point, I suppose I did something wrong during the update)
Then, new problem. When using /etc/fstab, the system said there was a 
problem.
And asked me what shell I want to use (you know, the question that when 
you have it, you know you should pray, because problems are only beginning)
Still, the partitions were all mounted.
i did fsck, but it did not pretend to correct errors on fs
So I try to look at the man... and there : more unfindable... as for 
less, make, sed, uname, ...
I know how to fix it using a cd. 
(http://lists.freebsd.org/pipermail/freebsd-questions/2005-January/073301.html)
Still, I need some precisions :
did I miss some entry in UPDATING ?
When I have everything fixed, should I make buildworld, buildkernel and 
so on from the beginning again ?
Would fsck -a correct my filesystem ?

Thanks a lot !

Grégory