As to whether or not you need a BBT thermometer--I also wondered about what the difference was. I've heard that they are more accurate, but from what I can tell, the only difference between my regular digital thermometer and my digital BBT thermometer is that the BBT one is pink. I did many experiments when charting and both thermometers always gave me the same temp. I have one friend who insists that the temp. must be taken vaginally, but most people I know take it orally. I did, and it worked out fine. I certainly can't imagine putting a cold thermometer in my vagina first thing every morning!
Good luck! Charting can be such a pain, but it is exciting when you start to see the patterns emerging.