You may or may not be lucky with gps. Both the cars we rented in France had integrated gps.
We didn't want to chance it for our rental in July, so we just got some France/Benelux maps for our Garmin. If you don't have one at home, and don't want to pay per day for one from the rental company...if you rent via AutoEurope, they will send one to you to take with you. I looked into it for us, but because it was to be FedEx'd to us in Canada (and returned via Fed Ex) and with the crappy exchange rate it was going to cost about $55, and we were able to get the maps for our own gps from Amazon for the same price.
I think GPS is essential...even just for mapping, keeping track of your speed, knowing how long you have until you get to your destination, knowing about traffic delays or alternate routes if there are detours. (Last time we rented, we hit some bad rain storms and local flooding...our route to our accoms was closed, so using the gps we were able to find an alternate). Some people do use google maps or whatnot on their smartphones. I don't know much about that as we don't own a smartphone.