Anyone can sue anyone(or estate).
You cannot make changes on a will in the manner you described.
You need to have an attorney to represent you in this matter.
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.
Attorney Pippen is correct. If you do not have an attorney, please retain one as soon as possible. Good luck to you.
This information is presented as a public service. It should not be construed to be formal legal advice nor considered to be the formation of a lawyer/client relationship. I am licensed in Connecticut and New York and my answers are based upon the law in those jurisdictions. My answer to any specific question would likely be different if I were to review a client's file and have the opportunity to interview the client. Accordingly, I strongly urge you to retain an attorney in your jurisdiction with respect to any legal matter.
The sooner you get an attorney to represent you in this matter the better. Otherwise you may have a big mess on your hands. Good Luck!