i've never touched my power steering fluid, i would guess you would be ok to top up if its low but i would guess at some stage it would be a drain and refill but you would need to look in Rave for the exact answer. i cannot stress enough to get yourself a copy of rave, its is far superior to mostly any other manual for any car i have seen.
as an idea i have attached a few pages below.
i like the inugel expert which at 50 % dilution would cost roughly £50
Motul Inugel Expert Ultra Engine Coolant 1 Litre | eBay
typical OAT coolant from halfords, again £50 roughly, you could purchase deionised water to be special
Halfords | Halfords OAT Antifreeze Concentrate 5 Litres[object Object]
View attachment 65821
View attachment 65822
View attachment 65823
in the manual where it says something like general electrical precautions, when you click on that it takes you to the relevant part of the manual.
basically 2 screws to drain, although one on the block is tucked away and i've never managed to find mine but haven't looked either, squirt with a hosepipe, one screw to bleed, although bleeding can take a while as you need to wait for the stat to open to be sure to get all the air from the heater as it will blow cold until it does.
your call really, the worst you could do would be not to bleed it properly and run the engine with insufficient coolant, over heat the engine which will do serious damage. in reality, as long as you keep it topped right up during the bleed and keep an eye on temps, its a piece of cake...
di i mention to get a copy of rave ??