Getting X running in RH 7.3, Radeon8500, P95f+

[yakkowarner]

I am installing (or just installed - not actually sure which is most accurate) Red Hat Linux 7.3 on a brand new system. I'm not running the most traditional set of hardware, so I could be having trouble at a number of points.
Motherboard is ABIT AT7 Max
No PS/2, so mouse is Microsoft IntelliMouse 3.0, keyboard is Logitech Internet Navigator
The keyboard has an exact match during installation; there is a Microsoft IntelliMouse/USB option, too, which seems good.
My graphics card is an ATI Radeon 8500, which is also listed during installation (and also in xf86config, which I later tried).

The monitor is a ViewSonic P95f+, and here may be the problem. It's supposed to get up to 2048x1536 max resolution (albeit at a reduced refresh rate), and I was hoping to run 1920x1440. So during the last stage of installation, I tried selecting 1920x1440 from the pull-down menu. Before I could even click "test", the screen went grey with black lines across it for a few seconds, and the system rebooted. Maybe it was trying to run the higher resolution at too high a refresh rate?

Then it wasn't starting X, and startx complained about errors in the config file.
After a couple of trips through xf86config (which doesn't mention anything about USB mice, though it does have an IntelliMouse option - problem?), I get a GNOME-like screen, but the mouse jumps around and causes the window (apparently in virtual desktop mode) to jump as well. Stuck. CTRL+ATL+backspace.

Booting off the installation CD and selecting "upgrade" doesn't return me to the X config screen at the end; can I get back there?
After doing an "upgrade installation" and selecting all the X, X Hardware, and Desktop packages, it booted into graphical authentication mode, but the mouse is still having the same issues.

Suggestions on where the problem might lie and how to isolate it?

[yakkowarner]

Manually setting the boot run-level to 5 rather than 3 failed because X didn't like its settings.
xf86config gave me a working file in the sense that the server ran, but it was unusable, with a jumpy mouse and screen.
But Xconfigurator actually identified my monitor as "P95f+", and, while it didn't list resolutions higher than 1600x1200, I now have a system that boots to graphical user authentication and works correctly with my mouse.

I need to know at least two things now:

1) What refresh rate is being used? I don't want to blow out my monitor. I know it can support 87Hz at 1600x1200, which is enough to keep my eyes at ease, but that's not the higest it goes at any rate, and I want to be sure the system is trying just 87 Hz.

2) How did this happen? Ok, I'm glad it's running now, but for future use, I need to know what's up in the config files and not rely on the "wizards". Obviously, I'll look around in /etc/X11/XF86Config-4 and see if I can figure out what happened, but suggestions on what I'm looking for (and what other files might be relevant) are appreciated.