How hard is it and what involved < remove engine etc > is it to swap the autos out of the same model TJ's

Pretty easy, if you have some time to invest and basic knowledge and right tools.

got all three ready to go but does the engine have to come out???

Nope, though you might wanna have some muscle to get the tranny back into place.
It's a bit more work pulling the engine, but easier overall. Doing it on the ground is no picnic.