There are better tree experts here than I am, but I have successfully planted 4 fruit trees--2 Montmorency cherry, 2 pears, here goes:
First, the hole needs to be 1 1/2 to 2 times as big as the root ball. An auger REALLY helps to dig the holes.
SECOND, work the soil until crumbly or even, till the soil removed to put it back in to fill loose. This will help the roots to spread. Put several inches of manure/fertilizer ONLY at the bottom of the hole.
Third. you can help loosen the roots, but don't overdo it. I didn't even try and all 4 fruit trees have been producing fruit, growing bigger and every year I get more fruit from them.
FOURTH, plant so that the bottom stem isn't buried or sticking up several inches from where IT IS IN THE POT. If it helps you spray paint the line and make that level with the ground when planting.
FIFTH, prune only during the late winter/early spring, which is....NOW. ONLY prune about 10%/year.
SIXTH, ONLY fertiize along the drip line, NOT next to the trunk in the winter like you are blanketing the tree. They don't like this.