I'm well-versed in Who, and I've seen "Ghost Light" probably half a dozen times, and I still don't entirely understand the plot. Mainly, I think, because some of the more random elements are holdovers from an earlier version of the story... which was really an entirely different story. But it's still very cool. And I adore Seven and Ace. But, really, when Seven is calm, that's when you have to worry... :)

"Remembrance of the Daleks" is something of a personal favorite of mine. It's also full of a million awesome continuity references you probably won't get if you're not familiar with the early years of the show, but hopefully that will not prove an impediment to your enjoyment.