1. The 845PE chipset should work with 800fb cpu's (some firms will release some new boards as a cheap 200fsb platform but nothing is changed in them compared to the older ones), depends on the manufacturing process (if the general quality of the mobo is ok) and bios too though. As it's Gigabyte the quality should be ok and bios too, cannot say for certain until someone have tried though =)
2. Yes.