By executing a General Durable Power of Attorney, the "principal" - the person for whom it is enacted - appoints you as the attorney in fact for any action that may be required to undertake on your behalf, with certain exceptions (like executing a Will).  Bringing a lawsuit on your behalf could indeed be considered to be one of the instances considered in its execution.  More information, though, would be needed.  You could bring both a PI and PD claim in the same lawsuit.  Consult an attorney.  Good luck.