First of all, great Marathon Man reference. I can almost hear the Nazi dentist's drill as I type.
I'm not going to get into risk models and linear no-threshold discussions, but radiation exposure is part of your everyday life. You've been exposed to external penetrating radiation and internal radioactive contaminants your whole life. It's part of nature. Your front yard has measurable quantities of radioactive Uranium, Radium, and Thorium in it and your food has radioactive Potassium. It's all natural. God put it there. We've all been exposed to it since the beginning of time, and very few people are concerned enough about exposure to it, to actually learn about it and make reasonable lifestyle changes to reduce their exposure to it. I can confidently say that most nuclear workers, including HPs [although some might argue whether HPs actually work], receive less radiation dose in a year from their job, than they do from the natural stuff that God put all around us.
Now, the nice thing about working in the nuclear business is that the NRC [a very thorough and intrusive regulator], requires us to keep our radiation doses ALARA [As Low As Reasonably Achievable]. No one requires, or even considers keeping our natural radiation doses ALARA. As such, it's a big deal to us whether you receive that extra mrem, because it hurts our ALARA numbers. In comparison, no one cares if you hang out in your concrete slab basement for several hours when you could be in a lower dose area. In short, since your doses are closely monitored and tracked, you may actually receive less radiation working in the nuclear industry than you would working as a fertilizer truck driver [or you could receive substantially more, but at least you'll know about it and understand it].
Your question was about what you'd be doing as a junior HP. The great thing about your job is that particular job is where the rubber meets the road in radiation protection. You're the guy holding the radiation monitoring device and helping everyone else to keep their doses ALARA. If there's anything scary about radiation [other than ignorance due to media disinformation and green scare tactics], it's the fact that you can't see it or feel it. A cave man can see a fire or a saber-toothed tiger and run away, but something invisible and undetectable that [in sufficient quantities] could kill you is a scary thing [for a cave man at least]. That's what HPs do. We measure radiation, establish rules to protect the workers from it, and monitor vigorously to make sure that no one gets any unsafe or unnecessary exposure. That's better than you get at home.
If we, as a society, were really concerned about a mrem increasing our chances of developing cancer, we'd all buy our children's caregivers radiation monitors and train them as HPs so that they could keep our kid's radiation doses ALARA. I don't see a lot of that going on. So, we as a society, probably aren't that concerned about a few extra mrem.
Good luck in your new career,
MGM