I didn't answer this before, because the answer is kind of long, although I'm going to attempt to make ti as short as a link...

Start here: http://www.phailed.me/2011/02/learn-lua-the-hard-way-1/

If you learn LUA, you'll be able to mod just about any modern game. LUA is pretty much the only language that my game uses, and I know very little lua (I'm terrible at it). I thought that what I might do, is strip down evo to it's very basic parts, and give that to you as a starting point. That way you have models, textures, sounds, etc already available to you, so that the learning curve will be softer.

However, if you do this, I'd like you to really commit to it. I don't want to feel like I've been wasting my time if you're not actually interested in learning how to do things. It isn't easy, but the more you do it, the easier it gets, and at some point, you'll have enough knowledge that you'll be able to do or make whatever you like!

IN addition to learning the basics of lua (via that link) I would like you to make me a design document of what you would like for your game to be like. It doesn't have to be extremely detailed, but I would like for it to cover the basics of what you would like for your game to be. This link isn't 100% applicable to an rts game, but it gives the basic ideas of what a design document should contain. http://www.slideshare.net/maxminhaj/game-design-for-beginners

The reason for making a design document is so that you have a goal. It may change over time, and that's fine. For example, the original design document for Evo was extremely simple, and just contained what I wanted to do. Well, after a year I had far surpassed what my document had in it, and at that point I changed it to suit my new goals.

Anyway, think it over and let me know if you would like to really get into this stuff. It's a lot of hard work, but it's also a lot of fun too :-)