It's not an easy task unless you really know what you're doing... and even then, it's still a pain in the butt to work with. vars you will be using are client.screen and the like. Procs you will be using will mostly be ones that you create yourself.

I suggest you just become a byondscape member (if you're not already) and check out http://developer.byond.com/hub/Shadowdarke/sd_Text. It'll give you a pretty good idea of how to do things (if you're able to read and understand other people's source).