Puddle of fluid could be rusted out brake line. The push real hard then break free, corrosion in master cylinder or one or more wheel cylinders.the brake locking could be wheel cylinder locking due to corrosion. You might be able to loosen the adjusters to free up the brake shoes. chock the wheels before doing anything so it doesn't decide to roll if you do get the brake freed up.Suggest finding a vendor who sells shop manuels for your truck so you can see how things are supposed to work and how to properly disassemble the brake system.(As opposed to the get a bigger hammer and pry bar method) If your real uncomfortable with attempting brake work haul it to a pro as bad brakes can get you hurt fast.