I'm going to defer to Underscore on questions of installing Debian, hopefully he can guide you soon and it will be better that the blind leading the blind of my trying to help.

As to booting, I personally prefer to use a boot loader like the simple SBM or the beautiful and quite eliquent XOSL. With either of these programs installed to hard disk you can just install the Linux boot loader to the Linux partition rather than to the MBR. Then if you want to install more systems, or change things, or delete and remove Debian altogether, you don't affect the other systems. That's not to say that if you're a grub expert that you can't use grub as a boot loader. But I've seen enough problems posted about it and lilo, I've elected to do things the easy way.