The front pads are an easy swap, all you really need once you get the truck safely lifted on jack stands is a pair of needle nose plier. The front pads are retained by two springs, you just slide the springs out and pull the pads. I changed the front at 45,000 miles and they still had about 10,000 miles left. I tow a small a-frame camper (2500lbs) and have seen plenty of mountain roads.
I just did the rear pads and they were easy also, you just remove the two retaining slider bolts and pull the pads. Just make sure to apply a small amount of high-temp. brake grease to the slider pins so they don`t freeze up. You will also need a c-clamp for both front and rear to compress the piston back in, but do this slowly and I always remove the master cylinder cap so I don`t blow out the cap seal or O-rings on the master cylinder. Make sure you re-attach the master cylinder cap and be careful when you first move the vehicle, the truck may not stop due to the caliper pistons getting back in place.
The rears had 67,000 miles on them and they were done, they still had some material left but not much. I used OEM Toyota pads as replacements and they were around $50.00 a set from the dealer. Brake pad wear really depends on how you drive your truck, but this may give you a rough estimate.
I hope this helps.