It depends, Yes and no. Theming isn't hard if you can use gimp or photoshop. However, I will say that editing smali is hard ( Talk to Shinru2004 for smali ). You shouldn't have to actually edit smali in most cases when theming. You get smali code by decompiling an APK with the SDK tools and you get simple XML's when you rather extract an APK using an archiving program such as 7-ZIP,WinRAR, WinZip Et Cetera. I will also say theming is where I started, UOT Kitchen to be exact as they have bits and pieces of great framework. Then moved on to editing color of pre-existing images and so forth. I would be glad to help you, As you seem more modest then the jump straight in and compile people I have seen around lately. What part of the phone are you starting on theming first?