Yes it will work.
Just reuse your old Hammer Axle and Control Lever.
The safety works with the hook on the Control Latch and the notch in the Control Lever's axle.
The decocker works with the tab on the old sear, but I am not sure if using decocking with the LEM will cause damage to the gun or not, so I advise to NOT use the old sear. As long as you have the new sear installed you can not decock. The lever will move down but nothing will happen. I would also spend the $10 to get a 5+6 detent plate, makes safety feel more solid by getting rid of the decocking position.
Also note that older guns (USPs for sure) using newer style hammers with the old style catches will cause the weapon to fire when decocked. A hammer drop may have the same result. For safety sake be sure to get a new style catch if your LEM kit does not have one. HK sent me one free of charge. See image below if you have any questions.