Their route planner page is an interesting mix of English and French, even in he English version, but it should do the work. You can even enter the street address you're going to and it will suggest possible routes.

The "Tickets and fares" page will give you the ticket price between any start/destination stations. A quick check shows one-way ticket from any station in Paris (a single zone tariff-wise) to either Neuvile Université or St Ouen l'Aumone Liesse or even Eragny Neuville (train from Gare du Nord) at 5.05 EUR.

I use this route planner often, actually, since it is very convenient even inside Paris. Hope this helps.