The temp sensor is situated on the face of the block along from the spark plugs, it will look like (as you say) a threaded bolt, with a wire to a plug that clips/pushes onto it. this just unscrews out of the block.

These are cheap enought, worth taking the thermostate housing off, this is situated on the side of the block., clean it all out and iirc you can take the thermostate out and drop it in hot water, see if it opens, this may be knacked.

Best before you drive it around, to check these parts are functioning properly, drain the water out, flush it through with a hose pipe to get any crap out. Check the thermo is working and go from there.

Last thing you want is to blow the head or worse if the water is getting to hot or not flowing at all.