Yep, we were also told to wait a year. It was a LONG year! It took us 15 months to conceive our first DD (naturally). I was 22 then.
Have you checked out Fertility Friend for charting? It's wonderful! (online - just google. LOT'S of information and support.)
And, I have always charted with a regular digital thermometer and haven't had any trouble. You could start with what you've got now, and then switch to the new thermometer in the next cycle. (don't use different thermometers in the same cycle - they can be out a little.)