Hi welcome to the forums
I was one of the first to get the A8N-SLI back in december and am an avid overclocker and regular here. If you ever have specific questions about overclocking this board feel free to PM me.
Here's a few tidbits to get you started
1. Asus probe died with bios 1007 and up, but not to worry Asus has just released Asus probe II and its much better than the original. Just search the motherboard forum for "Asus probe II" and you will find a link to download it.
2. SuperPI is what I use for quick stability testing, run the 4m or 8m test they run about 3min and 8min respectively and are a good quick test. Once you find the O/C that you want, run Prime95 overnight to make sure its 100% stable.
3. Make sure you enable the PCI and PCI-E locks on this board by setting HTT to 201 or higher in the Jumperfree section of the bios. The PCI and PCI-E settings in the Jumperfree section don't work, the only thing that locks the buses is setting HTT higher than 200. If you boot up at 200 and overclock using a windows utility your buses won't be locked and your system will become unstable at about 215+mhz
4. The best windows overclocking utility is Clockgen NF4, google for it. You can safely use this program to increase HTT in windows. I would recommend making all other changes like multis, voltages and ram timings in bios only, its much safer this way.
5. The memory divders on this board are in the DDR subpage of the CPU configuration page in bios. They are labeled as "Max Memory Clock"
DDR400 = 1:1
DDR333 = 6:5
DDR266 = 3:2
DDR200 = 2:1
These are used to run your memory at a slower speed than your HTT, these can be helpfull in getting a good overclock. As you will read many times here CPU speed is the most important factor, so if ram limits your overclock use a divider. Never let ram limit your overclock
6. Other downloadable benchmarking programs that you might want.
Aquamark3
PCmark04
Cinebench
Sandra Sisoft
there are too many to list
And that is one smokin rig your Uncle built you. You must be his favorit niece
Have fun, and ask lots of questions there are tons of knowledgable people around here that will help. And don't let post counts fool you, there are some really sharp people around here with just a few posts, and some real Noobs that have thousands of posts.