No, you can't use the stock sensor, because it's a gauge sender. You need a temperature switch. You can buy overpriced aftermarket ones that have a capillary probe that you stick in the fins of your rad, or you can do some junkyard huntin' to find one from any number of different vehicles for about two bucks.
I used one from an 80s VW Jetta... it screws into the rad on those models, as well as Audis, Saabs and some Volvos.. same switch. It turns on at 195 and off at 180 (if I recall correctly... the temperature is stamped on the switch in degrees Celsius. There are 180, 195 and 210 degree versions out there, so pay attention). Then, I went to Home Depot and bought a female brass fitting with the same thread size, and soldered it into the metal bleeder pipe in my upper rad hose (VG30). Some wirin' and a switch inside the cab to shut the whole thing down for deep water, and it's worked perfectly for two years now. Total cost, about five bucks.
I've never personally seen one of those capillary tube probes fail, but I've heard plenty of stories. It seems like a half-ass to me to be getting a temp reading from the rad fins instead of the actual coolant stream. Plus, at least here in Canada, they're about $50.
Oh, and also, I've been running two regular old 30A Bosch-style relays in parallel to power my Taurus fan since I put the thing in with no problems (low setting only). There's no need to buy some fancy ultra-high current relay **unless you plan to use the fan's high speed**, but do make sure that both relays have the same wire lengths if you go parallel.
Plus, junkyard shopping is fun!
S