Imaging concerns

We are currently running ZEN 6.5.
I'm interested in learning how to properly image workstations and
reimage PC's that are older and running slow. Refreshing them that way
rather than reformating & reinstalling everything on each PC. Here are
the questions I'm wondering about, mainly about duplication:
Windows licenses
Office licenses
Asset tag information
Computer names

I know I can rename a PC later and change an IP address.

Do you need to image particular makes and models of PC's? ex: Dell
Dimmension 2350 vs 2400
Can they be different partition sizes or hard drive sizes?
I've read something about Workstation Image Safe Data Agent?
What is Sysprep and when do I run it?
Windows SID? (I think I read that somewhere)
Anything else I'm not thinking of to take into consideration.

Any help or direction would be appreciated.
Thank you
Frank