Updating a Network

We have a network running Win NT4 with 23 clients running Win98. I want to look into the possibility of upgrading to a Win2000 Server/Win2K Pro set-up to increase security and performance. First off, I think I have the whole CAL thing under control, but where should I look to get a good package deal? I only need one CD of Win2K Server, one CD of Win2k Pro, but I need about 25 CAL’s or so.
What sort of resources are available to help someone through an upgrade, you know, checklists, guides, stuff like that? What order do I do the upgrade in to give me the best chance of not screwing anything up and to enable me to easily just scrap the whole idea and go back to the old system? Any ideas?