89lxsport50:
Squirt the threads with a little Kroil or PB Blaster penetrating oil. It will help to loosen the grip on the threads. FWIW, I used a small pipe wrench to get the old sensors out. A little dab of anti-seize on the threads of the new sensors (most come with this anyway) is recommended. Snug them down but don't tighten them like you are trying to seal a leak on the Titanic.
HTH,
Chris