Hi. You shouldn't use the offline tools if you're a DM, here's why:
1. Buy the D&D Insider. (very difficult to get a subscription, but I managed to sub this just a month before this post).
2. Get Fantasy Grounds (might work for Roll20, idk)
3. Parse all the data using tools available; in other words, download all the data on the monsters from D&DInsider.
4. Import monsters into the game super easy. Once you know what you are doing, you can drag and drop your fresh PC and your fresh NPC within minutes, and then simply click on their abilities to have them roll fully calculated attacks against calculated defenses.