I'm confident in my abilities to remove and replace the sensor. I don't have experience with the Ultimaker, but I also print with a Rostock Max which I built from the kit and have upgraded significantly.
My first idea was to remove the screws that hold the fans on. I got to that point, chickened out, and put the head back together again. I looked for build information online and found the open source files and looked through the assembly manual. Seems like it is a bit involved, but workable. I imagine that I will have to take the head of off the carriage, to disassemble it enough to be able to get to the set screw. I'll have a look at it now.
I guess I didn't fill out enough of my account information. I located in Southeastern Iowa.
Thanks for your help.
Steve