how simple is it to drain/flush the power steering system in a TJ?

It looks fairly simple. Jack up the front wheels. Disconnect the return line to the resivour and put it in a container to collect the old fluid, then plug the hole. Turn the steering wheel from lock to lock while keeping the resivour topped up. This should flush the old fluid out. Stop when the fluid coming out the return line looks clean.

Why do you want to change the fluid? It should be good for the life of the car unless it becomes contaminated or goes a dark colour from heat. We had hydraulic systems at work that never had an oil change in their 30yr + life span, just regular sampling.

Why do you want to change the fluid? It should be good for the life of the car unless it becomes contaminated or goes a dark colour from heat. We had hydraulic systems at work that never had an oil change in their 30yr + life span, just regular sampling.

at the last service my mechanic told me the fluid wasn't looking too good and suggested that i change it. it's not an expensive thing to do and i figure it's something simple enough to do myself and get a better understanding of my car.

at the last service my mechanic told me the fluid wasn't looking too good and suggested that i change it. it's not an expensive thing to do and i figure it's something simple enough to do myself and get a better understanding of my car.

Yes, why not, change it if you want to.
Easiest way is to not disconnect anything - use a large turkey baster (like a huge syringe) to take the fluid out of the reservoir, then refill it with clean power steering fluid. Will get most of the used fluid out. Drop the now used syringe thing into a clear plastic bag for next time. Repeat at next engine oil change and it should end up nice and clean. Don't run the engine when doing this, and try to get the new fluid in without air bubbles (ie put it in slowly).

I've never changed it, don't see a need to. Then again if it goes dark because of heat, I guess it needs doing.

At best you won't notice any difference, at worst you will introduce air into the system, resulting in strange noises from the pump.