To determine what board revision you have look between the second and third PCI slots. There You'll see silkscreened onto the board 'ASUS A7N8X' followed by the revision number.
The latest Bios's I'm aware of from the ASUS home site are:-
Rev 1.03/1.04/1.06
A7N8X an8b1003
A7N8X DELUX an8d1003
Rev 2.0
A7N8X c18b1003
A7N8X DELUX c18d1003
Note the diffference between the basic and delux bios versions is the use of a 'b' or a 'd' in the name.
Regarding your Barton, it's FSB is 166 but it seems you should be able to run it any FSB you like like any Thoroughbred B chips.
Be carefull with 512meg ram sticks though - some boards just don't seem to like running them faster than 133(266) and this can be a real pain if you want to optimise peformance by running you FSB and Memory in sync.
As for temperatures I find that 50 - 60 degrees celcius is fine if the CPU's running in spec but if it's overclocked then these temperatures can cause a little unstability in certain apps so therefore try to keep an overclocked chip below 50 for stability (thats just from personal experience though and you may get away with more)
One day I'll look back at my current rig the way I do my old ZX Spectrum.......Would have been interesting to say the least if Sir Clive had Bill G's business skills