You have to duplicate the lower third composition in the project panel and not just the timeline panel. If there are further nested comps containing the text, you'll have to duplicate those and replace them in the appropriate comps, but without seeing your file structure, I can't advise any more specifically.
Working with compositions is a pretty basic AE skill. Sounds like you really need to learn how to use After Effects! Start here: Getting started with After Effects
Don't put the text in the precomp, just the background. Then do the text in the main comp on the layer above the precomp. Once it's positioned, perhaps even animating the way you want, you simply duplicate the text, move it down the timeline, put it over the next instance of the precomp, and just change the text.
Yep, I'm definitely new at this. I have tried duplicating the lower third composition in my project panel and then using that new composition "lower third 16" is what the duplicated composition becomes named. When I move it onto the timeline to edit it though, it still edits the original. I'll look to see what nesting is involved. Thanks for the reply.
Yep, as soon as I finish with this project it will be STUDY time.
As guys above said - you should prepare yur work in a way that gives you aabbility to duplicate comps. But now -when you already started, you can use f.eg True Comp Duplicator script: True Comp Duplicator - aescripts + aeplugins - aescripts.com