ndiniz,
It's not just the holidays, it's also that some of your questions are difficult to answer unless we get a lot more information.
Is your external drive permanently attached to your computer? If so, you should probably make it your boot drive and chainload Windows on your internal drive when needed. If it isn't permanently attached you may be able to pick which drive to boot from by tapping a function key before the boot sequence starts. (On my box F12.) If that isn't possible, you have to change the bios boot order every time you want to boot Linux.
If you intend to run several versions of Linux, the question is which version of Grub that they come with. It's easy to chainload a Grub2 install from Grub legacy. It's much more difficult to start a Grub legacy install from Grub2, as Grub2 is slightly broken. Now, the *buntus use Grub2 while PCLinuxOS uses Grub legacy; consequently installing PCLinuxOS last and letting it overwrite the MBR of the disk is a good idea.
When it comes to the actual partitioning of your external drive, that depends on how you intend to use your system. Several Linux installs can share the same swap partition. But will you want to share data between Linux installs or between Linux and Windows? That may decide whether you really need separate /home partitions or whether you actually need a data partition instead? On a normal setup your home directory would be the largest one, but if you keep most of your data elsewhere it can be quite small and easy to back up - and then it certainly wouldn't need a partition of its own.
