Compared to most other concertos, no. But, it all depends on what your skill level is. If you can play 5 or 6 of the harder Beethoven sonatas, you could learn the 1st concerto (and, really, any of the Beethoven concertos, except perhaps 4, which I consider to be the most difficult) very easily. But, if you have only played a sonata or two, the C major concerto would be moderately challenging, I think, and would be good to learn for your instructional benefit. For other easier beginner concertos, look into Mozart, Bach and Haydn.
"Difficult" concertos, however, include those by: Brahms, Busoni, Chopin, Rachmaninoff, and Tchaikovsky (to list just a few). The Liszt concertos are, again, moderately difficult depending on your skill level, but not impossible.