I've installed rear lifts in my 125 and my former 122.
The 125 ( hydro ) was extremely easy. Attach the lift arm plate to the lift arm, slide it in and install the two 5/16-18 bolts.
The 122 ( gear drive ) was real
I had to disassemble the lift arm ratchet to get enough room to bolt everything together. Cotter pin was inserted with a very long pair of needlenose pliers and the cotter pin was bent over with a screwdriver.