1) I have the connectivity kit...do I need this to connect the samsung drive to my PC?
only for power, the samsung doesn't have a "modeb"
2) Do I need a boot disk (I don't have a floopy drive and the USB won't boot even after changing bios)?
A floppy disk is certainly easier, you need something that is writable so you can backup your current firmware (if desired as yours is a replacement)
3) Is the xtreme20 firmware the one I should use?
That is the current version
4) Next I would paste this key into the xtreme20 fw at 4000-4200, correct?
That usually covers it, make sure it is a replace, not overwrite.
I think a hex editor is better for this process as kdx has problems with the Xtreme firmware.
What firmware version is your Samsung replacement as some versions are harder to get detected (ms19, ms22)
Look for geebee's tutorial.