I can't seem to find many details about whether windows 8 still uses bootmgr underneath all that metro, but based on what I can see (having never installed it) I believe it does. There is a surefire (and reverseable) way to check however.
First boot to a live CD or USB of your distro of choice. Then, once booted, determine which harddrive you have Windows 7 installed to.
#ls -la /dev/disk/by-label
The first command will list the labels of filesystems linux can recognize and which partition they are on in the form:
Label -> /dev/sda1 where 'a' is the drive and '1' is the partition. Next run the following command to save the MBR (boot sector only, no partitions) to a file incase you want to undo these changes later. (Save this file to a thumbdrive maybe) [EDIT: make sure
/dev/sda below matches the output of
ls for the drive windows 8 is on, e.g., if
Windows8 -> /dev/sdc3 then use
#dd if=/dev/sda of=/path/to/safe/storage/orig_mbr.bin bs=446 count=1
Now use gparted to make a partition for windows 8 and go through the install procedure for windows 8. Afterwards, boot the live CD or USB again and run:
#dd if=/dev/sda of=/path/to/safe/storage/win8_mbr.bin bs=446 count=1
#dd if=/path/to/safe/storage/orig_mbr.bin of=/dev/sda bs=446 count=1
This will back up the Windows 8 MBR and install your old one (thus restoring BURG/GRUB/LILO/etc). You can now boot whatever linux you have on that box and attempt to do your bootloader's update / OS probe procedure. If Windows 8 is detected (or multiple Windows OSes are detected) then Windows 8 uses the same boot procedure as Windows 7 (called bootmgr) and you can continue to use your current bootloader. If not, then you may try to manually chainload it like you would for ntdlr and windows XP.