Doing a bit more digging around here and there I managed to find a good site for public transit information for the Paris area. The link is located here. Amongst other things it has English language PDFs of the transit maps for both the Metro and the RER.
With the amount of time I am going to have I am pretty sure I will be using some public transit choices external to the train pass I already purchased.
The site also has a route planner which appears to be useful. A note about travel planner websites. I have found them only marginally useful because it seems that when I go to a country and actually reserve my seats with my train pass the trips end up being similar but not really what the planner site has. The one I found for Japan seemed to be way off. The one for Sweden was closer though still not really exact. I was able to do what I wanted to do with the information from the planner so I guess that it told me a route does exist is probably good enough. I will mention if the planner is accurate in France when I find out.
In thinking about this I wonder if it is not because the people reserving seats for you almost always seem to do things very manually. They don't seem to plan trips as pick starting point A and destination point B and let the computer do it all even when they are using computers. I recall how manual it really looked in Japan. At least Sweden seemed less so but it was still not really a pick and click interface.
