Reaktor does have a steep learning curve - and the ADSR Master courses (two of them) are very good.
If you intend to learn it well, it will require a commitment of time and some frustration.
But, on the other hand, if all you want to do is put together pieces of other works and tweak a few things, it should not be too bad.
When you get in trouble, the Reaktor forums are great for that.
Or you can just use the thousands of free stuff without knowing anything at all.
There are two styles of building blocks in Reaktor - Primary and Core. Some people like Core, I prefer Primary. They are a bit different.
Primary is more like black box connections, Core is more low level.