Hiya
When moving up the plans you can gain a bit of weight when introducing carbs but if you stick to the plan that weight will come off again whilst doing the steps up!!
Please don't worry about maintaining, it's very doable. Have 3 meals a day and 3 snacks and you will be fine. You can even have 'bad evil foods' again. ;-)
Just take it one step at a time, I know I wanted all the answers myself but noone could really give me the answer I wanted. I found it helped to read maintainers diaries and see what they eat foodwise etc to make myself feel at ease.
Good luck hunni, you can do it!
x