Truck has been garaged when not used for most of its life so all the rubbers seem in very good condition and all the bells and whistles (electronics) seem to have never been used/played with.....apart from radio.

It was serviced regularly by the agent.

My question is.....what needs doing (engine, radiator, trans, brake, power steering etc) and what fluids go back in? Should somethings be left alone?

I have read for example that the engine can be cleaned with an engine flush additive and then 5W30 oil put back in. Is this best for this age truck and temp?

What about the other fluids?

All and any information gratefully received.