Creating characters

This is kind of a tough question, and I'm just figuring out how to answer it. My game is an FPS, but I wanted it to include some RPGish elements - specifically, 'leveling up' in that if you hit people with your gun a lot, you get stronger, but if you shoot them instead, you get more skilled. Plus persistent stats like the total number of kills scored by the character, or battles participated in.
Also, there are additional features. For example - when you start up the game, all you can do is load a character. When you do that, you get pushed through to a character menu, which is different for every race a character can be.
My first trial run just saved characters off as text files. When you load a character, the scripts just set a bunch of global variables based on the information in the character file. When scripts need to do something (like load the character menu), they look up the global var. I'm having second thoughts about this system, but the problem is, I don't know any other way to do it. It's obviously wide open to client-side hacking; players could go in and edit all their character's values, which would make it no fun for other players online. But I don't think there's an option to store characters except for client-side. I guess that means encryption. But that's still not secure, right? Meh.
Apart from that, it's just sort of a clumsy system for loading and unloading characters. I thought of a whole lotof things I want to be able to do, such as swapping characters in between missions... and this system doesn't seem to cut it. I guess that a whole load/unload character script sequence would help. One that somehow clears everything that's going on, pops all the GUIs, then reconstructs everything with the correct character (race) settings. Seems like a lot of work, though :P.