System screen rotate - how hard is it?

[skyfish]

I wonder how much work is required to rotate the screen? I'm asking because I'm wearing Sansa Clip in a manner of a watch.

Is it simple like swapping x & y somewhere or would require a massive change? I know some C, but new to RB, slowly learning the code (not the lcd area yet). Could you please nod in the right direction and maybe share an idea or a tip?