To replace the pressure valve is simple. It has to be reached from under the car. It is located on the bottom of the ps pump. If I remember correctly it takes a short 17mm wrench to loosen the valve, then all you have to do is unscrew it by hand and replace with new one , retighten. You don't have to remove the pump for this, and ther are on o-rings to replace if it is only the valve leaking. I just did mine a couple months back. Took about a hour.
Good luck