That's how I did my first thermal diode reading. I eliminated the system thermistor attached to a Winbond w83697hf, swapped a resistor, added a cap, and ran wires to the back of the socket. Interestingly, the BIOS interpretted the temperature correctly, where as MBM need to be told that it was now a diode.
But, without that datasheet, you are screwed. You need to be able to identify the correct IC pins. You need to know what kind of circuit the IC can read.
It will be faster and easier to add the popular
LM90 from National Semiconductor ($3 from Digikey). No board needed, just use a couple pieces of electrical tape to attach it to (and insulate it from) the back of your motherboard. Run six wires and you're done.