instrument cluster questions

[GMCrazy]

i found an instrument cluster for my truck, but it needs some work. the truck i pulled it from had another temp guage mounted below the cluster, suggesting the factory one didnt work... is there anyway i can test it? btw, my motor doesnt run yet, and if it doesnt is there anywhere i can get another temp gauge? also the guages have rust, the outside is faded and some of the paint has rubbed off, the needles dont have much orange paint left, and is there anywhere to get the (dont know what it's called)very back piece that runs the appropriate power to the gauges? it might sound like crap, but im very happy to have found a free one! all advice is always very appreciated!!