Since Windows still does not offer means to skip rewriting the MBR, what can I do before reinstalling Windows to get Grub2 back into the MBR as easy as possible? (I'll also appreciate it if the answer then describes how to restore Grub)
Some people have been able to get NTLDR to chain to grub: http://stringofthoughts.wordpress.com/2009/04/27/booting-linux-from-ntloader-windows-bootloader/
Although in practice it's easier to use a live CD. I usually do something like:
mount /dev/sda2 /mnt/somewhere # mount the linux partition chroot /mnt/somewhere bash mount /proc grub-install /dev/sda2
Nothing. Just make sure that you have a live CD around. After you install Windows and by the way let it overwrite the MBR, just boot into the live CD and restore Grub.
Regarding restoring Grub, it has been asked before.