Since I suspect your 2 questions are related, I recommend reviewing some basics.
First, GRUB has to be installed knowing where it's "home base" (/boot directory) is. This gets "hard-coded" into the boot code that goes in the MBR--or sometimes in a boot sector. Suppose that you tell the grub installer that /boot is in the second hard disk, 1st partition. If you then do anything that changes the order, then you have to re-install grub.
For a bit more, look at the booting link below.
Can you now boot into your Linux install? If not, can you boot from a "live CD"? Somehow, we need to see the output of "fdisk -l"