I am extremely unfamiliar with installing Linux on a PC with EFI. Do I just make sure there is a FAT partition mounted as /boot/efi on a GPT partition table and use GRUB2-EFI or its it more complicated than that? What YaST options do I need to set?

Are you dual booting with Windows 8 ?

if not just blank the whole drive and do a normal std install of OpenSUSE 12.3

No, with Windows 7 Home Premium SP 1 64-bit

repartition the drive and install grub on the first LINUX partition
leave the MBR alone -- let win7 have it
you might also want to remove the OEM hidden "recovery" partition
this can cause problems( with linux and with windows) and if windows7 gets a virus then it is VERY likely the "recovery/repair" image is also infected

for that you would want a Microsoft install dvd
it is ( or was ) free from microsoft
-- i ordered one from MS , and it was free .They mailed it to me using USPS

partition it something like this

sda1 --MBR and windows 7 ( C:\\ drive)
sda2 -- linux boot partition " /boot"
sda3 EXTENDED !
sda4 /
sda5 SWAP
sda6 /home

and set the linux boot partition as the one to boot from in the bios

Is it as risky to leave the recovery partition on it if I'm installing Linux on a 2nd hard disk?

only to windows
and you will need to pay attention to how grub is being configured
that "recovery" partition can cause some confusion for the installer
as in thinking that windows IS on the recovery partition and not where it really is

The only danger is GRUB booting to the wrong Win partition, right? If it is, I've seen that before and can fix that pretty easily.

How do I put the Windows 7 option back in? I don't see any EFI images.