Can you give a link to the motherboard? ECSGF800A does not exist.
1. Yes. IDE and SATA either one would work. After all, we used IDE a lot longer than SATA has been around.
2. As long as the IDE drive works you should have no problem. Heck, most of the computers working today still have IDE optical drives.
3. Without being able to check out the board online I can't give you a definite yes or no. However, AM3 is rather recent, so the board should work with SATA natively. Win7 has no problems with SATA at all. "Switching around the boot order" makes little sense unless you mean having it boot from the optical; if that is the case there will be no problem. Both my wife's and her mother's computers use IDE opticals and I installed Win7 to SATA drives on both of them.
I have a question though... how are you going to use DR2 with a AM3 board? AM3 is DDR3 only. AM3/AM2+/AM2 boards use DDR2. You might want to make sure that the stuff in the barebones kit you are getting will all work together.