Find a bike shop that will include a bike fitment set-up as part of the purchase. They put you on a trainer and take measurements, then adjust the seat hight, angle, front to back position, as well as stem length, angle and handle bar rotation.
$1000-$1300 will get you a decent bike, but if you plan to do enough riding that you're going to be doing 100km rides, after about a year you're probably going to want a better bike.
As mentioned above pinkbike.com is a good site. You can find some pretty good deals, just finding the size frame you need is tricky... for example this is an awesome bike that's pretty close to your price (new it was probably $2500+) bracket but just a bit too small http://www.pinkbike.com/buysell/1357649/