you should check out the fixie/ss board for more info, but you could take off the current cassette on the back, and thread on a fixie cog and a bottom bracket lockring as a quick fix until you buy a wheelset. You might want to put some locktite on the threads too, just for added security.

ps-you definitely don't want to try to get the right side of the bottom bracket off...ever. they are put on insanely tight from the factory and from what i hear you need a special tool to put a new one in. and since they're french nobody has replacement parts anymore either. if only peugeots weren't so sexy, it'd almost be annoying working out all these problems with them.