Put the assembly (without top bearing and plastic guide) on chassis, push upper (802143) Servo saver with your thumb and lower servo saver with other finger then slide the e-clip with your left hand, halfway is enough to holds it. Then use your plier to settle on the clip.
Stand up while you push down the servo saver and make sure your chasis is completely flat on the table.

Yes.. it is not an easy thing to do. My thumbs still "in red" by now.

Maybe if you have a small vice or small C-Clamps it would be helpfull.