Honestly, I could not disagree more than what the other answerers have given. Sure, you will get dirty, but do not start out by getting a repair manual if you don't have a car to work on or have the knowledge. A repair manual can say: Torque cylinder head bolts to 65-70 ft. lbs. in the sequence given if figure 63. If they said that, would that mean you would do that without knowing why? My advice, get the knowledge of how they work first and then get deeper into what parts do what for the car. A good website is to go to howstuffworks.com and they have a whole section dedicated to under the hood of a vehicle and how it works. Everything from oil pump, camshaft, crankshaft, thermostat, cooling system, lubricating system, pistons, rods, bearing, valves, gas, and so on and so fourth. There is so much stuff going on under the hood of every vehicle. But learn about basics first and then go off and start doing minor repair on your car. Minor being, changing battery, adding coolant/water to your radiator if needed, changing oil if you feel comfortable. Don't start with hard things. That's what I did, I started off small and worked my way up. I still learn new things about a car everyday but I do have many knowledge about vehicles and it's great. A good first step, start with the basics of how a car starts and then go on from there. It's awesome... once you stop, you will love it. You will make many mistakes, you will get really mad but that happens to us all. Good luck!
Also, get involved with some classes they teach. Take it slow. And if you can, get some car friends or mechanics and talk to them. Just don't feel stupid asking questions. And when you have a car to work on, always follow your repair manual. You may think you know how, but I couldn't tell you how much times a simple job I thought it was turned out to be such a problem without the manual's help.