No you can't use the 333Mhz chips, but they are still at least 4-6 weeks away, you can only run the 266 (133mhz) chips.
your board has a AMD chipset, so it will not overclock very well, but that does not mean don't try
But get a Athlon XP between 1600+ and 2000+ and make sure you have a good heatsink, I don't know what you are upgrading from so you may already have a good one.
Just update that BIOS first, and have fun