I think that you need to be good at using your graphic design program. A lot of graphic design involves modeling/materials/rigging/animation. But theres more than that too.
Then theres scripting. In my opinion your not going to be changing the source code. Your going to be using scripting objects in blueprint and extending existing classes. You will also be creating your own classes.
I know what variables, if statements, functions, loops, arrays, and what the concept of a tick is. I know how to model/rig/animate and apply materials. I think its going to take more than that though.