Accomodation is the toughest thing. If you can't get it by yourself within a few days of trying, I'd suggest you go with a package.
I don't believe it's too late to get B&B accomodation through Le Mans Hotel Reservations (+33-243-200-700 or
lemanshotelreservations@wanadoo.fr), and any ticket you want or need through a broker like Just Tickets. Car hire is easy, Orbitz or somesuch, same with flights.
That's great you've decided to go. You'll love it.
