The game is really split up into two games but they have nothing in common as far as story goes. Choose the timeline/game that you want the walkthrough for then you'll be taken to sub-menu with all of the missions (each "level") in that timeline.
At the beginning of each mission's walkthrough you'll find a chart with information regarding the enemies in the mission. Such information includes: an image of the enemy, number of enemies of that type in the mission (on later missions enemies regenerate, therefore the numbers are based on a first time through basis), and the enemy's name.
Now thanks to me and my 1337 Savestate hacking skills I'll finally be able to get AP values for the enemies! Unfortunatly, to be able to provide you with the most accurate information in terms of AP values and how many enemies have X amount of AP, the enemy chart at the beginning of each mission is now huge! Thanks go out to Kero_Hazel for taking the time to disassemble the ROM and search through it to try and find the values for me. Thanks Kero! :)
I suggest that if you're unfamiliar with the Gundam universe you vist the Story page for some background information on each part of the game.