My 5.7 Liter Hemi's cooling fan is sticking on more and more often. Even when cold, the fan runs full blast. It's noisy, and of course, it's an unnecessary drag on the engine. Before I replace it, is it serviceable? Can it be lubed or is there a thermostat that may have failed?

Also, is this a DIY job? Can an average home mechanic replace this fan with decent, but modest hand tools, or is it a job for a pro?

Jim