When you think about the sheer number of strings in a piano – multiples per key, remember – and the tension to which they are stretched, you realize that there must be a colossal amount of force trying to break the piano in two. This explains the need for such heavy construction – a frame of cast iron is needed just to resist the tension of the strings. It also explains why a professional piano tuner can be an important person to call if you need piano tuning.
It is tempting to compare tuning a piano to car maintenance – you can do it yourself, but you may feel more comfortable putting the risk in the hands of an expert. However, the situation is even more important than that, as the process of tuning a piano is far more complex and takes far more patience than most ordinary vehicle servicing. Changing the oil or the spark plugs is nowhere near as involved as tuning two hundred or more high-tension wires.
Attempting to tune a piano yourself is certainly possible, but there is a range of knowledge and skills that only an experienced professional will have. One aspect of this is in understanding the current condition of the piano. Since you are reading this article, you may have a piano that has sat around without maintenance for quite some time, and the cost of professional piano tuning seems prohibitive. However, it is precisely this kind of piano that can be dangerous, as a neglected frame may have started to develop weak spots that increase the risk of the entire structure collapsing violently in on itself. You would not want to have your hand inside a piano when this happened. An expert piano tuner can recognize the danger signs much more read than you will be able to.
Having said that, if a piano technician has confirmed that your instrument is in good shape, you can certainly begin learning about piano tuning yourself. If nothing else, it takes patience. It can be very easy to give up part of the way through tuning and ruin the whole process. There are also various skills that must be picked up along the way, such as the piano tuners' method of setting the pins in such a way as to promote tuning longevity and prevent the piano from sounding sour for as long as possible. Piano tuning certainly takes effort, but it can also be a rewarding process, and maybe even therapeutic.