Seals are probably shot. Replace the pump/reservoir assembly.
Replace the whole rack, it would take speical tools to replace seals
Clean the power steering are real good check for where the leak is coming from and go from there. For example if a hose is leaking replace hose, if power steering pump seals are leaking replace pump, exc.
you can, but you will blow the seals in the steering ,and then have a bigger problem that you have now
In general, repairing a steering gear is not recommended for the casual mechanic. Rebuilt steering gears are available at a reasonable cost. A leaky pitman shaft seal is indicative of internal damage. The seals do not usually fail without something else acting as a catalyst. You'll be far better off if you just replace the steering gear. And while you're at it, check the hydraulic fluid for any contaminants. If anything is floating around in the power steering pump and/or the hoses, it would be a good idea to replace them all since it will just cause the new parts to fail prematurely.
The hydraulic seals in your power steering will be eaten away by engine oil. Your power steering will start to leek and eventually, it will not work at all.
Where is the leak? From one of the hoses? Replace it. From the pump? buy a rebuild kit for $12.00 and rebuild your pump or buy a rebuilt pump for $50.00 and swap it out. From the steering gear box? Remove it and replace the seals or replace it with a rebuilt box.
it will cause you seals to ware out
generally this means that the seals are worn and either need to be replaced or could be more cost efficient to replace then entire unit.
most likely blown seals or seized valves in the steering rack.
The oil is bad for your seals in the pump as well as the hoses. If you have oil in your power steering system you should have it flushed as soon as possible.
I would say most likely HEAT! Does the power steering unit have a cooler? When you changed the power steering unit previously did you replace, not replenish, replace the fluid? Usually pwer steering pumps run a long time but once the fluid gets contaminated, either with dirt, debris or the lubricants are cooked out of the fluid then the fluid doesn't keep the seals soft. When the seals get hard the unit leaks and sometimes whines and squeals. I have added Lucas Power Steering Additive to some power steering untis that were on thei rlast legs to get them to last awhile longer. It's about $10.00 for a small bottle but it did stop leaks. If your power steering unti is out and you are going to replace it, look into adding a cooler to it, a small condensor that will remove some of the heat from the fluid. Or you could maybe insulate the power steering unit with some sort of insulation material. The power steering unti sometime sits very close to the headers or exhaust manifolds which helps deteriorate the fluid. Power Steering fluid is one of the most overlooked fluids. Many of today scars use transmission fluid for the power steering fluid and if you ever have a transmission get the fluid all hot, you will soon be replacing or repairing the tranny.