for LFPN you really need to buy the larger scale Paris TMA map. Getting into LFPN unless you come in from the West, is a bit of a nightmare, first time round VFR. There are one or two strange reporting points, you get funelled in very low (1500' QNH), and things happen very quickly after passing Pontoise. Additionally there are several small fields near the route between Pontoise & LFPN that can throw up some traffic into your face.
The RER from Versailles is about half an hour, and the taxi from the airfield is about £8.
Bon chance!