It's good that you have an understanding of what your skill level is. However, you will also learn by trying new things, so don't be totally spooked by the idea of doing mods. Just start small. A wheel/tire change, a motor change. A suspension modification. I've been preaching "Walk then Run" for a while now, and I'm glad to see you understand the concept, but don't let if keep you from expression. Your paint work looks pretty good, and you build pretty cleanly. Those are the basics and you seem to be mastering them well. Keep it going.