1) It is correct what Betaray points out. The is a manual with the CD. Perhaps not the tech tree you wanted, but it tells you what you need to research in order to get the stuff you want.
2) EMP missiles can only be build by Plymouth, and since you were hit by 1 I guess your at either Eden campaign or Eden Starship. You can defend against these in many ways, but the most effective is by researching observatory and meteor defense. Build both an observatory(in base) and a Meteor Defense building (where you need to defend). The Meteor Defense will shoot down inbound missiles, as long as they are not launched in pairs or three's(only in Multi Player)
3) Best defense for you colony, is the location. You can have all weapons researched and have loads of defenses, but at wrong position in map you will still encounter problems. Having said that, lets look at you line of Guarp Post (GP) as you mention.
1 line of GP's are not very hard to get through. 1 way of strenghtening you line of defenses is by having 2 lines of GP's.
You must also pay attention to what kind of GP's you use, and wheter you GP's are connected to Command Centre with tubes. As Eden I would reccomend using Acid Clouds and Emp's as GP's. For Plymouth ESG and Emp are the best. Also, have you ESG GP's fire where enemy is approaching as vehicles will take more damage when they drive towards the ESG GP. In your GP line Emp GP's should be placed as every 2nd GP.
As for Walls, you must have in mind what kind of weapons you have availible. Laser, Microwave and Rail Gun, all need a clear line of fire. Meaning they cannot fire over walls and buildings. Weapons such as EMP, ESG and RPG, can all fire over walls. Looking at the combos I mention earlier, those weapons can all fire over walls. You should always build walls infront of your GP's, if your weapons availible allows them to shoot over the walls.
