diff --side-by-side with_freshrpms without_freshrpms > diff_freshrpms and look at the file diff_freshrpms .... items with a "|", "<", or ">" are different (so are installed by freshrpms).
I think I may have dodged a bullet here. Doing exactly as you say, when I got to this stage, there were no entries in the diff_freshrpms file that had a "|", "<", or ">". I checked both with a visual inspection and by running searches for all three characters in my text editor. I'm assuming that means I'm safe and I don't have to worry about my system having undesirable RPMs from the freshrpms repository.
Thanks to everyone for giving clear and helpful instructions.
Dave