Question 1 - It is very likely the statute of limitations expired, barring the claim for your mother's death. The survivor's statute of limitations for wrongful death is two years from the date of death. The estate's claim is also two years, however, it is tolled while the estate is unrepresented for up to 5 years. There is also a 5 year statute of repose for medical malpractice claims. This is not an opinion on the value of your case and you should really talk to a lawyer for an exact answer on statute of limitations.
Question 2 - You should consider contacting an estate lawyer. A good place to start is the lawyer that drafted your mother's will. To be enforced a will must be presented to Probate Court, proper notices given to heirs, and Court procedures followed. If you do it yourself, contact the Probate Court and determine whether anyone was appointed as representative of the estate. Information and official forms are available at gaprobate.org.