Hi Kathryn

That's great that you're working from the archived HTML classes - I hope you're finding them easy to use and understand.
Let's see if I understand your question, and if not, please don't hesitate to let me know...
You're wondering how hard it is to move content from an existing/templated website to whatever new fabulous digs you create?
The content you'll be adding to either one would be text and images, which is pretty much a matter of copy/paste and placing the images, etc. as you like them. So, not that hard at all.
The thing about a template is that it gives you a design or a frame with which to work, so you're just adding in the 'filler' elements (the important stuff like text and your logo) and so you can avoid dealing with the more complicated design elements for now. Assuming you design your own webite at some point the only thing I can imagine you'd want to take with you to the new site would be your own content and any images you've used that you really like.
Let me know if I've missed what it is you're asking here...