Dodge RAM 1500 maintenance - suggestions?

Hi there --
I have a 2003 Dodge RAM 1500, and someone told me recently I should get the timing belt and water pump replaced (even though there's nothing wrong with
them - or anything else on the truck - as far as I know).
Is this advice I received correct? Should these items be replaced in the course of normal maintenance even if there's nothing wrong with the truck?
I was also advised to change out the transmission fluid, power steering fluid, and rear differential fluid on a regular basis.
I have the oil changed every 3k miles and all the other fluids checked, but I've never had these things flushed and had all new fluids put in.
Do you agree that this should be done regularly for all vehicles? How frequently should these fluids be completely replaced?
Thanks for any information you can offer -- I'm fairly old but have never heard of anyone replacing these fluids and parts as normal maintenance, so I'm curious if those more knowlegable than me agree with this.
Happy Thanksgiving --
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