Here's were it can get tricky. Of course the correct way to replace this is to completely evacuate the system and remove the evaporator but with a little ingenuity you can have it replaced in 10 minutes.

Open the evaporate shell by splitting the halves. I used a spring clamp, backwards, to help me hold the halves open.

Using a long pair of needle nose pliers, gently work the Thermistor out of the evaporate fins.