1. Timing belt change does not absolutely need anything else done. It is however a very good idea to change the timing belt idler, timing belt tensioner, and timing belt idler stud. The belt, tensioner and idler are generally bought together as a kit. The idler and tensioner can seize with age and if they do goodbye engine. When the timing belt is off it is about 20sec extra to replace them
2. Water pump might live to 300,000klm, might also fail tomorrow. Many people have very varied life for the pump, I guess it depends on belt tension, number of starts and how the car is driven, and the coolant you use.
3. Water pump is about 10 bolts and some silicone to replace when the timing belt is off. This is why many people choose to do it at 100,000klm. If not figure 4 hours labour at a workshop if it fails (ie as big as the 100,000klm service). They are very cheap if you go holden rb30 aftermarket ones.
4. Power steering fluid is generally expected to be in there for life unless something is wrong. If you do want to change it, undo the resoviour lid an carefully undo one of the hard lines that go into the steering rack. Wait 10 min for the fluid to drain then retighten the line. Fill the resoviour, start the motor and turn the wheels from full lock to full lock a few times. Top up resoviour. Any auto transmission fluid will do.