USually they take maybe 20 minutes once you get the fan out, they are pretty easy if you can get to them. Just run a couple bolts through it to make it totally mechanical
fan clutches are usually super easy. If it's on your 4.0L then you usually have four bolts on the block that hold the entire fan assembly tot he block, then there's four more bolts that hold the fan to the clutch. Basic hand tools (7/16" I believe) is all you need.