Jim, you can take the RER train to Gare du Nord and then transfer to the Number 5 Metro. I know coming up the RER at Gare du Nord there is an escalator. I would think that there are escalators also to get to Metro 5 and then at
Republique station.
Here is a good
description of how to make the trip. I believe it is 8,40 Euros for the ticket. You can use same ticket on Metro.
