I find this to be a very interesting episode, though mostly because I was fascinated by Inca, Aztec, and Mayan culture as a kid.
This episode is plausible--ish in the paranormal factor, but completely unrealistic in the security factor. There are multiple occassions where people are messing with the 'Incan Princess" exhibit, like stealing stuff from the sarcophogas, messing with the mummy, etc. A Museum would not have that much of a lack in security, even is a small town like sunnydale. If they're big enough to have a museum, that museum has security. Minimum of gaurds and cameras. Besides which, the mummy princess is left TO OPEN AIR. This is a MUMMY. Special conditions such as humidity, temperature, and light must be taken into consideration, in which case the sarcaphogus would be ENCLOSED by like plexiglass or something. *sigh* But if all of those things were taken into consideration we wouldn't have an episode. Hollywood. Yay.
As for the plausible-ish paranormal stuff, curses on tombs were very common. I would imagine that royal tombs from all over the world, not just Egypt employed curses in the protection of their dead. This however is a unique case.
Supposedly this princess was sacrificed to...please the gods and protect her people, as far as I can gather. Ward against the darkness. Now, sacrifices for the Inca were a religious matter (though also used to reinforce political power), and it would have been an honor to be sacrificed for her people. She would have been inundated with how great an honor it was from birth, as it was a part of her culture. The character we get is oddly quite 'modern', resentful of being sacrificed. Not very fitting, though I'm sure there would have been acceptions to the norm.
However this episode has the curious quirk of having a ward or charm to keep the sacrifice dead. Essentially keep her from rising again. Not unprecedented, but unusual. And while it may be that I haven't researched enough, I don't think it was a tactic that was really employed by the Inca, especially not for honored royal dead. Destroy the seal release her on the world again....well, seal gets destroyed but she is also prevented from draining the life essence from living beings, so she is destroyed as well. Yay, no dead Xander.
In notable, series-relavent news, this is the first episode we see Oz! Yay Oz! One of my favorite non-vamp characters. Played by Seth Green, yes Seth Green, same guy that creates Robot Chicken and voices Chris in Family Guy. Love Oz! :-P Back tomorrow for Episode 5!