Well, it's not impossible to learn--I'm living proof of that--but it is difficult. You need, at the very least, a good tuning hammer and mutes, and it's best to have someone teach you. The best situation would be apprenticeship to someone who has been doing it for many years. I didn't choose that route, and unfortunately I have had to learn by trial and error, and a lot of reading. I have had to deal with broken strings, notes that just won't stay in tune, difficulties with hearing well enough to tune the extreme high and low ranges, and a lot of other things. A lot of pianos that need tuning also need various small repairs, which most professional piano tuners are able to do. If you're just trying to get your piano in tune for less money, just call a piano tuner. By the time you get done paying for the tools, books, and fixing any problems you may have inadvertently caused, it will probably end up costing you a lot more.