I would definitely have the trans repaired rather than putting in a used one. While it's out you might as well change the clutch packs and check clearance on front bushing.
My memory is coming back to me, I think. The rear solenoid is used for kick down and the front, which is on the 722.358, is used for the upshif delay during warm up. Maybe somebody can confirm this.
The bottom line is they can be interchanged, but you should look into repairing you original rather than risking it with a used one (I'm assuming that it's used, is it?).