Read the link: That Bios flash is there to add support for the newer 1333 FSB processors. If you have a 1066 FSB processor it'll still run on 1066 timings. Unless, of course, you tell it otherwise.
Regarding your RAM: You are nearly always able to insert faster RAM into your system and run it, provided it is of the correct type. It will simply run at the default settings your Mobo/Bios have. In the case of PC2-8500, you'll normally boot to an 800Mhz default. Then you would have to go into the Bios, tell the computer to run the memory at 1066 (533Mhz apiece x 2 = 1066), and see... Be a bit cautious: If you have an overclock going already it'll drive your RAM that much harder as well.