"***Fixed***
In the future, if anyone wants to know how to do this, it is super easy. Download grubfix32.sh from repo.powerprogress.org/debian/install/grubfix32.sh and copy it to a USB flash drive formatted as FAT or HFS. Use the Debian CD to boot into the rescue mode, mount the root partition (for me, it was sda3), execute a shell prompt, and run 'chmod u+x' to make the script executable. Then, run the script './grubfix32.sh' and point it to your boot partition, which, for me, looks like this: './grubfix32.sh /dev/sda2'. Let it do its thing, reboot, and then you can proceed to edit your sources.list and add whatever snapshots you want, as long as they are newer than the image you downloaded to do the install. For example, the DVD image I used was generated in June, so I would not be able to use a repo from December of the previous year.