Since the usage is approximately 500 miles per year I wouldn't do preemptive repairs unless I suspected something was starting to fail.

I would definitely replace the bad fan clutch with the Behr.

If choosing to do the belt it will need a tensioner soon after as old tensioners aren't happy once they are disturbed. If doing the belt and tensioner, replace the bearing bracket and the two small pulleys, one is grooved one is smooth. Febi should be fine for these. Spin the alternator and the AC compressor clutch by hand and listen for noise/condition, both have replaceable bearings.

Water pump brand, try to get a MBZ remanufactured pump, the old one is needed as a core.

As a recap, I'd do only the fan clutch now with the Behr but go farther if something else was presenting a symptom of future failure.

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