Juan,
The first thing about a 5.1 mix that is most challenging is the monitoring setup. Providing you have 5 full-range speaker enclosures of the same type along with a suitable sub-woofer and they are all positioned and calibrated, the next step is to create an I/O setup that supports surround routing. You have to figure out which convention you'll be using (i.e. L R C LFX LS RS or L C R LS RS LFX, etc.) and then you need to do your routing for the session. The most challenging part is the surround panner which, from my understanding, was never accessible in Pro Tools but there are joysticks that support tactile control of such panning. So, in a way, yes, it's accessible but quite complex.
Slau