If you have not done this before a few tips. Depending on the tool you want clean access to pull down on the spring. Being able to pull down straight will help removing and installing the keepers. Some cars I unbolt the master and lay it on its side. Do the harder to get ones first. Cylinders 7 and 8. Your arms will thank you later. Take a rubber mallet and rap the edge of each retainer 3 or 4 times. I do it as soon as the rocker shafts are off. Doing that loosens the pinch between the keepers and retainer. Good lighting. Lay rags to prevent a keeper from dropping into the engine. A small pencil magnet helps at times. I also find it better to wipe oil from the keepers and my fingers when going back together.