My '89 740 GL wagon has over 200k and her latest task for me is to repair a power steering fluid leak (quite aggressive).
From the research that I have done so far, I have seen successes stories on rebuilds.
My question is:
Is it worth doing the rebuild over the replacement, and how difficult is the rebuild?

There is a difference of about $60 for a rebuilt replacement and the rebuild kit.

Has anyone done this?

I would say if you feel confident enough to tackle the rebuild yourself and your happy with putting it on your car etc... then i would go for that.

If you have doubts about whether you'll have the right tools etc... do some research into what tools y ou ned for the kit, see if you can find any online tutorials and such.

Failing that if your not confident then go for the ready-rebuilt one. That way you can always keep the knackered one for future reference, maybe even re-build it as an experiment test.

Matt