That depends on what is causing the problems.
If the red steering wheel icon is lit at the dashboard, then there are some different causes.
If its the little electro engine mounted on the PAS steering collumn its easy to replace that motor (you need to have the number on the CPU on the steering column to replace that motor).
But it can also be in the steering column (CPU or angle sensors).
And then the problem may be only solved by replacing the whole PAS steering column quite more difficult to do (athough described in hayness shop manual)
Frederik