get a livecd, (gentoo-minimal install for example) and boot using this cd. this would allow you to mount your /boot (or if it is on the root partition, /), then you can edit/vieuw all your files. since /boot/grub/grub.conf is still a text file, you can open this with your favorite text editor (nano, vi, vim, emacs, ...)
best use a small livecd like gentoo since it takes less time to download/burn.
don't dispair, all the above steps are really easy.