The cap screws that hold the caliper are torqued to 80 ft-lb. To remove them, you will likely need somewhere near 140 ft.-lb. They are beefy screws and can handle this torque.

The problem is that you cannot.

When you are underneath the vehicle, it's almost impossible to apply 100 ft.-lb. torque. The only way to do it is to lie beneath the wrench and force it upward. It's not possible to do it while attempting to force it downward.

Don't be afraid to use a 24" extension. It will need to protrude forward underneath the front bumper. You may only get the bolt to budge due to lack of room, but, that's all you want. It's preferable to use two men for this. One on the end of the bar and one holding the socket on the cap screw so that it does not come off while the torque it applied.

Most of the larger parts stores can get the caliper at a reasonable price. Should not be more than about $80. or so. AutoZone is probably a decent bet.

You can also consider these fellows:

http://www.brakewarehouse.com/