Check over on Class A in the RV.Net board. Scott (handle is Fireup or Fire-up). He removed a corroded temp sensor on a QD7500. Posted good pictures of the process. Might pick up some ideas from his thread.
We had quite a bit of work done on our QD8000 recently. Added a new Temp Sensor, but then also added a A/B switched in second Temp Sensor clamped to the hot water end of the manifold. This way if the stock one goes out, I have a chance to keep running the unit under temporary B Temp Sensor. (Yes, possible risk, but I've had two stock Temp Sensor's go out in two years. Last time was in Bishop at 110 outside. I knew the coolant was good, and the oil was fresh - just another faulty Temp Sensor. So I went with the A/B option, to allow emergency temporary usage in such conditions. Willing to take that chance.)
07 Country Coach Magna Rembrandt 45' ISX600
Roo II was our 04 Country Coach Allure 40'
OnDRoad for The JRNY! Enjoy life...