I was a certified NYS EMT-B and I volunteered.
As a person who is scared of contracting blood-borne diseases, this risk is constant in every health care field, whether you're a first responder or in the clinical setting. Since you're currently in the nursing track, you should know that PPE is your best friend. It is YOUR responsibility to protect yourself before entering the scene and treating the patient. On a side note, I agree with ticklechin, that your chances of catching Hepatitis is higher than HIV/AIDS. You should have your vaccinations up-to-date if you are working in a high-risk environment. It would be naive to think that you would not be at risk for anything working in the neonatal department; You just never know what can happen.
As for administering "mouth-to-mouth," there is a device that helps facilitate. There is a one-way valve that prevents any back flow and thus, protects the user.
It is very fast-paced and stressful, as every situation is never constant, never the same. There are ups and downs... As a first responder to the scene, your job is important. The care you deliver can greatly effect the positive outcome of the patient at times. Also, you must be able to communicate efficiently and effectively. You must be able to get information from the patient and you must be able to report vital information to the ER staff.
An EMT-B (EMT Basic) does not have the advanced skill set as an EMT-C (Cardio) or a Paramedic (the highest level). Depending on your state of certification, even the EMT-B responsibilities slightly differ (in NY state, EMT-Bs are allowed to administer activated-charcoal, asthma neubulizer/inhaler medication, Epi-Pen. In other states, an EMT-B cannot perform these procedures by law).
In the course, whether you're taking the fast-track or regular course, you will definitely be able to get a good feel if being an EMT is for you. The certification examination process is a two part test, consisting of a hands-on practical with scenarios and a written part. In addition, you must complete a certain amount of hours either in the hospital ER or on an ambulance ride-along.