This is a few years old now, but I’ve only just stumbled onto it. This lecture from N. T. Wright is easily the best brief introduction to the theology of St. Paul that I’ve ever heard. At three quarters of an hour, you could have a quick listen on your lunch break, or, it’s so rich that one could probably listen to it half a dozen times and really engage with it, taking notes and so forth. Either way, do have a listen. I know you’ll enjoy it!