Spiderem -- since your fan's always on, the easy option would be to install a switch in the cockpit that lets you manually control the fan. That way, you can turn it on whenever you see temps climbing and turn it off whenever you don't want it on. This would avoid (or delay) the need to tear into your car to replace the sensor.
Here's a recent thread on other oil temp sender options with lower temperature triggers
http://forums.pelicanparts.com/porsche-911-technical-forum/1039954-lower-temp-switch-3-2-oil-cooler-fan.html --