Ideally you could do with an answer from someone with experience of this exact problem. I suggest hunting down a Gigabyte specific forum and ask if anyone has been though this procedure (updating Rev 2.2 with Rev 3.0 BIOS), and if so, what came of it.
Of course you could just go ahead with if you don't mind buying a new motherboard if the BIOS procedure goes pear shaped. If the board is still bootable after the update then you
should be able to flash it back with the original BOIS.
If the board is NOT bootable after the update then you have a big problem. You would have to buy a new BIOS chip to replace the dead one, which may be alot harder than it sounds (finding the chip). Another opion might be to buy the exact same board, boot it up and try a "hot swap" of the BIOS chip then flash it. The latter would one scary procedure though, and I have never done it myself so I couldn't give you any details. Other than that you would have to just buy a new board and scrap the dead one.
Please note: I am NOT recommending you try this without knowing what will happen.
Cache.
