Is it possible to change the sides on just one shipped map? for example, if i wanted to put the 212nd on Utapau only, is it possible?

Yes, it is possible. It requires you to munge a new mission.lvl (with your 212th sides called in the Utapau scripts) for the entire game. Replace the game's mission.lvl with the new one. I'm pretty sure this right, somewhat.

That's not necessary. You can just create a new map like normal and change the addme.lua for that map so that it changes the shipped Utapau.