Hi guys, I am very new to ati, was always nvidia to the grave

So I have the HIS 2900XT 512mb DDR3 and I want to flash it with a modded bios. I can overclock 100% stable to 870/2400, made a 6pin pci-e to 8pin mod, but I want to try 1.3V with some higher voltages.

So what would be the best way of flashing, do I need to backup my original bios first (how?), do I need to edit my own bios or can I flash with any XT bios..? Can I change Fan speeds..?

What do I use to flash the card..?