I'm not reluctant to take on tasks for which I should call a professional. I also end up calling a lot of professionals to fix what I've screwed up. However, there are some simple tasks that virtually anyone can handle themselves with a little knowledge and a few specialized tools.
One of these is changing your own oil. Even with a coupon, a full oil change with new filter runs close to $30 at the oil change shops in my town. The last time I changed my own oil, I was able to buy the oil and filter for half that much. The change took 15 minutes. I'd like to find more ways to make $15 in 15 minutes!
The tools needed are few: a medium-size adjustable wrench, a wide, shallow plastic pan to catch the draining oil, a plastic funnel, and a oil filter wrench shouldn't set you back more that $25 dollars, and can be used forever. A few rags will come in handy.
The parts you'll need: oil (the type and amount of oil you'll need will be found in your owner's manual), an oil filter, and a new washer for the drain plug. You'll find expensive, high performance oil for sale, but for most driving, the less expensive stuff is just fine.
The process is simple. On the bottom of the engine, oil collects in the oil pan, bolted to the bottom of the engine block. In the oil pan is a drain plug (a bolt) usually 9/16" or so. When the engine is cool, remove the oil cap from the top of the engine and place it where it won't be lost (I learned this the hard way). Then wriggle under the front end of your car (a sheet of cardboard will help you slide and keep clean) until you can fit the wrench onto that drain plug. Position the pan under the plug, then, lefty loosey, carefully unscrew the plug. The oil will start to flow, some on your hand, so have a rag ready. Put the plug where you can find it!
After the oil has drained away, usually a few minutes, find the oil filter and fit the filter wrench around it. Again, lefty loosey. Once you've turned it a little, you should be able to unscrew it by hand. Caution: The filter will be full of oil, so empty it in the plastic pan. To put on the new filter, dip your finger in the oil and lightly oil the rubber gasket on the bottom of the new oil filter, then screw it into place. Do not force it on; if the filter doesn't screw on easily, back it off and try again. Tighten snugly.