How did you know what to call the different kernels?
I just made them up, they should be what the kernels are actually called. You will need to rename them so that all three aren't named vmlinuz or whatever, or grub will be confused. Doesn't matter what they are called as long as each has a different name.
Do I have to move the kernels to /boot?
No, you don't, but It is a lot easier. And I should say just copy them, so you have backups.
You can specify which drive and partition they are on using "root (hd0,0)". Grub counts from zero so (hd0,0) is actually hda1 (where your /boot is, right?), and (hd2,5) would be hdc4 ( I think...ha ha). You also need to keep in mind that some bios's need the kernel to be located in the first 500MB of your hard drive. In my opinion it is neater and easier to have all your kernels in the same place.
Again, safer to copy them than move them as I first mentioned.
You will need to mount /dev/hda7 and /dev/hda8 to access the kernels (assuming you have redhat booted at the time), cd to where each kernel is, then simply:
cp vmlinuz /boot/deb_kernel
Remember that vmlinuz may not be the actual name of your kernel, and you can change deb_kernel to whatever you want.