Rosetta: Exchange Rate

How much money should I bring with me to France? I think I bring $1000, in Euros of course so more like 700€. Perfect. Oh wait, I have a couple of hundred dollars left over, maybe I'll just go ahead and bring that too and I can change it in to Euros when I get there no problem. <----This all went through my head before I got to France. Once I got here I had enough Euros to live on for a while as well as a couple of hundred cash to change into Euros at some point or another no hurry. Well, when we landed in France one of the first things I did was look for a money exchange booth, they can be found practically everywhere in the Paris airport. Practically everywhere that is except for the path between the arriving flights, the luggage pick-up, and the exit. So, seeing no easily accessible money exchange, I shrugged and figured I'd just change my money at any bank whenever it was convenient. One month later, here I am in Le Touquet, I have my very own bank account and find that it would be nice to change my dollars now (I have a week left before my first paycheck). So today I walked my dollars down to the Poste (this is the name of my bank and it doubles as the post office). When I arrived they told me no problem, they could change my money. A couple of minutes later the man comes back and tells me that they don't take $100 bills. Um... Okay, is there someone around here who will change them? You'll have to go to a bank (here I got a bit confused because I was under the impression that the Poste is a bank but maybe not...) so I went to a bank. "Sorry, we don't change money, you can try the Poste. Oh, you've already tried that? Well try the LCC down the street." So I went to the LCC, "Oh no, we don't change money, try the Poste." At this point, I realized that it was useless. I am going to continue trying on my to Belgium, I hope to find a train station that will change my money... or maybe somewhere in Lille. But who would have though it would be so difficult to spend my money. I tried the library too but they don't open until 2PM today (who knows why) so I am headed back there. In the end the only thing I accomplished this morning was mailing a letter and finding out that the post office will hold a package for 2 weeks for me (remember that my bank doubles as the post office so this was all very convenient), this was good news as I am expecting a package but will be leaving town for two weeks, so I've got my fingers crossed that it will all work out.