How much food should you be eating if you are trying to maintain weight?

That really depends on your personal circumstance eg gender, height, age, weight, activity levels.

You could try myfitnesspal, set your profile to maintain, fill in all the details and it will give you a daily allowance. The daily allowance will likely seem a lot if you've still been eating fairly light recently, so you may want to increase your calories slowly until you find the maintenance sweet spot.

I agree with the above poster - it's trial and error. Some people can eat 2000 calories to maintain, others can only eat 1200. You'll have to track your calories for awhile and adjust up or down to find your maintenance range.