As far as getting the nutrition info for a recipe, there is a great program called MasterCook that will do that for you. It's inexpensive and you can store and print all of your recipes. You can also use Fitday for that by entering the ingredients on a blank day, but that's a little clunky.

What I do most of the time is measure things BEFORE I put them together. Let's say I'm going to what you did, and mix some vegetables into bottled marinara or whatever. Usually I will only prepare enough for that one meal, but let's say I'm planning to get two meals out of it. I would put one tsp of olive oil in the pan, add, say 1/2 cup raw mushrooms, 1/4 cup chopped onion, 1 cup shredded spinach, whatever, and saute. Then I'd add 1 cup of the sauce. Half of that mixture is one serving, half goes in the fridge for the next day. Because I measured the components, I don't have to figure out what the whole is worth from scratch.