I just changed out my thermostat on my ranger today. It's located on the front of the engine just above the water pump. If you follow the upper radiator hose from the radiator, it will lead you right to it. You'll see the housing for the themostat attached to the end of the hose. There are 2 10mm bolts holding the housing on. Getting to them is another story. You might not have to take anything off to get to the bolts, but in my instance, I was changing the water pump anyway, so I had the fan and radiator out of the truck. This made getting to the thermostat very easy. Again, you might not have to do all that, it was just my case.... I hope this help. Oh, have a new gasket and sealant(gasket maker) handy along with your new thermostat before you tackle this project.
Thanks for the help from the above answer. It made a hard job easier. I remember when a thermostat was a 10 minute job--goodbye to that. Following the upper radiator hose told me I was in for more work than I thought. The housing and the 10mm bolts are almost hidden from view and access is nearly impossible with all engine parts in place. I only needed to replace the thermostat which had froze open in very cold weather. I loosened the fan cowling, serpentine belt and removed the fan--all were serious obstacles to the thermostat housing bolts. I used a six inch ratchet extension (or combo of) to reach the bolts. Position the fan cowling for max access and put a towel over the top of radiator housing to protect your arms--it is sharp! Once the thermostat housing was free I pulled it inside and above the AC lines to remove and replace the thermostat. I found replacing the thermostat housing bolts was very difficult because the 10mm socket would fall out due to access angles needed to start threading them on. I finally used the 6 inch ratchet extenders, without ratchet, to get it done finger tight. A small peice of tape (invisible will do) around the socket and bolt head was invaluable in keeping the bolt from falling while getting it in place for threading start. I then attached ratchet to extenders to completely tighten the bolts. Reassemble and tighten all loosed parts. Thermostat works!! Major miracle for a non-mechanic.