replacing oxygen sensor on 2006 Kia Spectra

Should the engine be hot or cold ? I have heard mixed reviews.... The sensor is located in an easy place to get at and I am considering doing this myself. Any tips appreciated. Thank you.

2 answers
I like to remove them hot, I try to get paraffin wax to wick down the threads of the sensor as I try to take out the sensor, works great. Make sure you don't strip the threads and are patient taking out the sensor!
I always thought warm was better than cold, not hot, but warm. A little heat seams to allow the threads to break loose easier.