Now, Tomas. Have you actually ordered this harp or not? If you haven't, then you need to locate someone with a harp and ask them to let you try it. You could find that you don't like playing the harp at all - that you don't like the feel or the fact that the strings are vertical rather than horizontal as in the dulcimer.
However, if you have it and like it, then the people who tell you to get a teacher are right.
I learned this stuff by trying harp every day for a week under a good teacher. I learned that it is just not my instrument. I also learned that Sylvia Woods' books are held in low esteem. Our teacher said that her fingerings are illogical and that she doesn't finger the same notes the same way two times in a row. Having heard my teacher's incredible playing and having seen the way she got other students going, I believe she knows what she is talking about.
Sylvia Woods books are nice to have for the pieces in them, especially because you can get together and play with friends. But I wouldn't use them for technique.