To remove the hose you disconnect the hose per this picture. Using a clip to hold the spring and spring holder out of the way helps with the process.
Remove the spring and spring holder from the hose. Be very careful with the spring as it tangles easily. Then pull the hose through the neck toward the head. You may need to twist the hose if it catches on the body.
To remove the neck insert us the key that comes with the insert. It will fit into slots in the insert.
Remove the insert and install the new one. Re-install the hose. Again you may need to rotate the hose as you install it. Then re-install the spring holder and hose. The hose needs to come out of the faucets, through one side of the spring holder, through the spring then back through the spring holder and attach to faucet. If the spring is twisted it will not work properly. Make sure to twist the hose until the spring is working correctly.