I have to say that if you have difficulty with the definitions and basic intuition of fiber bundles, you probably don't have a great future in high-energy theoretical physics. Fiber bundles are the foundation of modern approaches to gauge theory, which is ubiquitous in high-energy theory. Any junior or senior math major should be able to grok them with little or no difficulty (speaking from experience: I learned them from a physics book as a junior). I can appreciate that an engineering grad might not have much experience with comparably abstract math, though.