most of the G2 questions I get asked have to do with removing the mechanisms from inside (which is a PAIN)
other things to address - how to remove gems (I just use my needle nose pliars to pop and scrape), and size of replacement gems (flatbacks are easiest to find that small in the most colors - if you know somewhere that has the same kind of gems that g2s use that also has a variety of colors, please share)
really , aside from the eye gems and the ones with moving parts, they're the same as any other pony...