Hi Mona,
I weight train 2 times a week (hard training!). I also box and kick box and I think the combo of cardio and resistance from punching and kicking stuff is really great for toning.
For the eating while you are at work, I def. recommend fruits and veggies. Sandwiches are great, Wonder bread makes a light whole wheat bread that is 80 calories for 2 slices!
This makes me happy! I like sandwiches. You probably have to bring most of your meals with you. Do you have a locker to keep items in, a fridge and a microwave at work? I have never worked night shifts like you do so I'm not sure what meals would be. You can always bring a bag a spinach, a hard boiled egg, a tomato and some light dressing to make salads. I also like Amy's Organics which makes a whole line of delish frozen foods. Eat Right (from Safeway) is a pretty delish brand too.
Snack bars are great for when its not meal time, I like Kashi bars, FiberOne Bars etc. Maybe go to Trader Joes or Whole Foods and check out some of their snack bars too.
Drink a million gallons of water a day. I keep a 32oz container at my desk and I try to drink 2 of these while i'm at work. I also have green tea for when I want some flavor. Crystal light and other flavor packets are pretty good too. I try to only have one soda a day (or less).
Good luck!