Will Google SketchUp work? If so, how do I then add skin, animation, and abilities to it? And then finally put my model into the game?
I don't think sketch up will work. After you model the units you have to skin them and rig them (rigging only required when you want the unit to "walk"). Then after that you need to code them. Coding is what actually puts the unit into the ga,e. Along the way you will also need to make icons and insert them into the compressed icons file, and you will need to make text entries for the in game unit- i.e. name of unit, description etc. Honestly, I suggest you either find a tutorial for modeling and just start with that or else get a raw model from someone and try skinning it yourself. Making even one unit from start to finish takes a lot of work and time (at least 10 hours I would say). There's about 6 different programs you're going to need from start to finish.
mbmcdon;5406679 There's about 6 different programs you're going to need from start to finish.
Are all of these programs free?
You can find free versions of all of them. Just start going through the maser sticky looking for tutorials or ask Warb Null if he knows of a good one.