Brakes leaking fluid and not working properly

The vehicle listed above is the Limited model. My rear passenger side brake pad was grinding and someone still drove it even tho the brake fluid was getting low but not way bad. There was a lot of play in the brake when pushing on it and it would hardly come to a stop and felt like it had to catch on something to brake to stop.
well needless to say the pad wore completely (they thought they heard something at one point I'm guessing the test of the pad) now all fluid leaks out and there is nothing but air when braking. In fact the vehicle does not stop now. Somebody said the brake pad wearing pushed the caliper and while doing so I think they said the "caliper seal"wore and is why the fluid leaks out
So do I just need to replace the pads and caliper and seal? Also would I have to replace both left and right of caliper since they are pretty costly?
Also, what all do I replace and what tools I would need?