A Nissan clutch has four parts: the pressure plate, friction disc, the flywheel and the throw-out bearing. If the factory maintenance schedule isn't followed, or after a number of years of wear, the entire clutch may need to be replaced. It's a difficult job that requires you to take apart the transmission and other engine parts. You'll need a lot of tools, including a replacement kit, and a manual to guide you through the specific steps.
The owner's manual for the Nissan is not enough to walk you through the process of changing a clutch. Because there are so many steps, it's highly recommended that you have a manual with you, especially if you're not a professional mechanic. Which manual you have will depend on the model and make of your Nissan. "How to Keep Your Datsun/Nissan Alive: Maintenance & Repair" by Colin Messer is a great book but it only covers Nissans up to 1987. The Haynes Repair Manual will work for models after that year.
There are many tools for the job you'll need. You don't want to be caught without the tool you need and no way to get to the store because you took apart your car. Check the manual for specific tools based on the model and make of your car. You'll have to have the right size socket wrenches to get the bolts of the transmission off. Extensions will be very useful to reach the out-of-the way spots without breaking your back trying to loosen them. For all clutch replacements, you'll need a replacement kit, which will have at least the clutch disk, the slave and master cylinder, and the release bolt.
Since you'll have to put your car up on a jack stand and get into the bowels of the engine, it's worthwhile doing some other car maintenance while your changing the clutch. For example, while you're working underneath the car, you can drain the oil pan. All you have to do is slide a catch pan underneath the oil pan and loosen the plug. Then, while your working on the clutch, the oil will drain. You can also take this time to replace the transmission fluid and add more grease to the flywheel bearing.
