It took me 3hours to do the spheres not hard but a little messy!The spheres tend not to leak but as I understand it they have a diaphram that seperates a gas from the fluid and as you go over bumps the diaphram moves absorbing the bumps hence when they go the ride becomes hard!!As they go down hill gradually you do not notice how bad the ride is until it is terrible and new spheres seem like a new car!!
Get youself a new car,change them!!