Such a good idea,
1 yes they can share swap
2 you can install grub on mbr hda1 and add to /booot/grub/menu.lst some entry to choose at boot time either slack, Débian or win
3 home partition can be shared but it's a little complicated for install
4 you don't need a boot partition it can stay in /
5 in modern times, you don't need to destroy to built again : )
6 i think grub is easier so why would you still use lilo?
7 I dearly suggest to download from here http://www.nl.debian.org/devel/debian-installer/
and install with it. It's sarge the would be stable release.
The installer is quite simple. It wille show your partition to choose the target and propose every option. You can install with home and add your actual home in the fstab later. I favor instalation with only two patition for home use one / and one /home so you don't loose config if system crash.
Have a nice try : ) Marc A