Congrats on the new job!! I, for one, LOVE working night shift. There are less doctors, administrators, families, etc. around and I think the night-shift staff are a lot more laid-back. I work 7p-7a (3 times a week), so my schedule is a little different than yours. If it is my first night shift of the week, I try to get in a 2-3 hour nap before going to work. That way I'm not dragging when 4 am comes around. After that, I take a shower and sleep for 6-7 hours as soon as I get home from work, then I wake up and start the routine all over. On my days off, I usually go to bed around midnight and sleep in until 9 am or so. However, I don't have any children, so it is much easier for me work the night shift. I don't use any eye masks or anything except close the curtains and make my room as dark as possible. I also rely on tons of tea or coffee to keep me up throughout my night shift.
Finally, I think if you lead a healthy lifestyle, your immune system will be just fine and you shouldn't worry about colds or indigestion. I have been working night shift for the last 4 years and have never had a problem!