I did the half dome trip last year. According to the Smith and Fletcher scale I'd say that one is difficulty 1C or maybe 2C. Just so you have something to compare with.
On Smith-Fletcher scale 3, 4 and 5 you'll encounter almost vertical terrain, but the cables are anchored every 2-5 m, so if you fall you will not fall far. And if climbing is too difficult you just pull you b*** up using the cables.
I'd advice you to start out with a route classed 1-2 in difficulty and work your way up. Probably you'll realize that difficulty 3 is easily within your reach.