Widescreen resolutions and ATI drivers

[Charles Malespin]

Hi all, I just got a Dell 2005 Widescreen monitor.  I want to use the
1680x1050 resolution that the monitor is capable of, but I cant figure
out what to do to my xorg.conf file so this will work.  I have looked
around on the forums, and some people said to install the ATI fglrx
drivers.  Well, seems that there are two how-tos on installing them,
which one do I use?  Do I need to install these drivers?  I have an ATI
X300 card which on the dell site says should be able to run the monitor.
I tried to mess with the xorg.conf file and then messed things up so
that X wouldnt start.  I fixed it, but I got fairly lucky so I would
rather not have that happen again..  Can anyone walk me through what I
should add to my xorg, and if I need the ATI drivers?  My xorg.conf
still has my old Dell 17" as the default monitor, so obviously I need to
change that, but I dont know to what..
Thanks in advance, 
Charles