We don't know much about hour composition. It sounds like you are making work for yourself by setting up a green background that you can green screen. This is a very inefficient workflow because AE will generate an alpha channel for your text, it will look better, and there is no work at all involved in laying the text over a video in a NLE.
Usually the first cause of extremely long render times in CC is the use of AE's Ray-traced rendering in a comp when your system does not have a GPU that supports this feature. If you are extruding the text, then I'd suggest a different workflow. Create your 3D text in C4D lite. Your system does not support Ray-traced rendering so it's going to be very slow.
Tell us more about your composition. Tell us about your render settings. Show us a screenshot of the comp with changed properties revealed (select all layers and press the U key twice) and maybe we can help a little more.
The actors were already shot on a green screen because they had limited set space but want to put them in front of a large background. That's actually a comletely different issue as I haven't even included that video in the comp yet and, when I do, I just have to replace the green with plain white. I was just performing a test to see how long it would take to render the 3D text.
As you guessed, it is extruded text. I was suspucious that my GPU is too old to handle it properly.
I'll give the C4D lite route a try and see if it renders in less time.