Tranny temp gauge for ZF6?

OK so if you've been following along, you know I just got this truck and of course I am finding out about it's past life as I go thru it. One of the things I discovered is that the "oil temp" gauge it has in the 3-gauge pod (also has pyrometer and boost gauge) is actually a temp gauge for the ZF6 trans. Do I need this? I never heard of monitoring oil temp in a manual trans. The reason I ask is the sender leaks and I want to know if I should get another sender, or take this gauge out and replace it with something else? If replacing, what would be the best thing to monitor?