The pivot at end of the dipper stick is made up of long stepped bushings. They hold the "coupler" in place. The pin passes through them & the bucket ears. The trick as Mitch said is balancing the bucket on the open hook so there is no weight on the pin. It is easiest with two people, but if no safety police present, you can reach through the open back window to curl the bucket. You can feel when it is hanging freely from the hook.
After you swear a while at the !@#$^&*()_) snap ring, & the @^*()& snap ring pliers that keep slipping & get it out, the pin will slip easily.
Lay one bucket on the ground upside down, pins toward you, pick up the other.
If you don't have extra hydraulic valve & plumbing at the dipper, it's going to be a big deal to to add the hydraulics & it adds significant weight to an already poorly balanced tractor.
Mine with Ehoe & a hydraulic thumb was best with a very large weight in the front bucket.