Hi,
Sounds like a cool project. There is some sample code for angular control of stepper motors at LucidTronix: lucidtronix.com - lucidtronix Resources and Information.. They are using a potentiometer to control the sensor but it wouldn't be to difficult to adjust that code to work with a temperature sensor, just change the range of values that are getting mapped to the angles. Also I think they are using the same motor as you, 200 step, bipolar.