I'm a rookie and I have no experience trying to diet while working nights. However, based on what I think, eat as you would normally if you woke up at 6AM to work first shift. To me, eating a breakfast based meal is most pleasing when I wake up. You may decide to do the reverse. Anyway you decide is okay I think.
Moving on. Losing weight is a calculation. The easiest way for me to describe how to know how many calories to start with is to go to MyFitnessPal, fill in your information and then set your exercise to zero (or sedentary I can't remember which it is). This will give you a rough estimate of how many calories to eat to maintain your current weight. Therefore, (example) if it say you need to consume 2500 calories, subtract 300-500 (the more the faster you'll lose obviously but maybe at a cost of muscle mass) calories and that would be a good number of calories to start with.
As far as what to eat, obviously, avoid things high in sugar and fats. I would recommend a carb cycling type diet if you are able to follow such a thing. Example, I currently do the follow:
70g of fat every day.
50, 50, 100, 150, 200, 250, 500g of carbohydrates, then repeat (Starting on Monday)
275-300g of protein every day. (some would call this amount extreme, but this has been working for me in order to grow strength and muscle with minimal if any fat gain.)
I would suggest doing something similar without such a huge jump on Sunday.
Using an app, or notebook to count and log all of your food and macros I find very helpful, especially when you forget and need a quick meal plan for the following day.
My stats are 5'11" 194lb (weekly average because it will fluctuate a lot) approximately 8.0-8.5% body fat and I maintain this fairly easily and I cheat too often. If I were to eat clean 100% I would lose around 0.5-1lb per week.
I hope this gets you started, or if you want something more constant, I would suggest eating around 100g of carbs a day and 75g of fat, topping your caloric intake off with protein. Like I said earlier, that baseline number is the most important step.