Where can you mount the oil temp sending unit? The one I have now came mounted in the oil pan and I can seem to stop it from leaking.

Aren't they usually near the oil filter remote mounting? I believe it is the small orange wire in the newer harnesses.

It can be mounted in the remote oil filter assembly as long as the assembly is electrically grounded to the engine. This is assuming that the filter is on the hot side of the oil cooler. Some have been changed to be on the cool side of the cooler.
Mine are in the oil pans and I haven't had any leakage issues.