I have never seen a case where the executor didn't have to show up, although I suppose it is possible.
This is not legal advice nor intended to create an attorney-client relationship. The information provided here is informational in nature only. This attorney may not be licensed in the jurisdiction which you have a question about so the answer could be only general in nature. Visit Steve Zelinger's website: http://www.stevenzelinger.com/
You are wondering if someone may begin to serve as representative of an estate without being sworn in by the Register of Wills. I agree with the previous answers. Normally an executor must show up at the Register of Wills office to be sworn in. However, there have been cases where a representative of the Register of Wills office has gone out to visit the executor/ executrix who might be home bound. In that case the attorney might go to the office to start the process. Also, if the executor/ executrix resides in a different state, the local Register of Wills will deputize the Register of Wills of that other state to administer the oath. You are calling from Ambler and if you are referring to the Register of Wills of MONTCO, you will generally find the staff in that office are very helpful and might also answer your questions.
You categorized your question under the heading "contesting a will' so you may have some underlying concern about the will and/or probate. As an intestate heir you do have rights during probate, and you have even greater rights if you are an estate beneficiary. You have the right to be notified of the probate, the right to contest the will if you feel there is a valid reason for doing so, and the right to see papers that are filed during probate. If that is the case, you might want to consult with an attorney. As you already noticed, it is true that some things happen during probate that are not easily found in Pennsylvania law or handbooks. The information is there but sometimes difficult to find. That is where the services of an experienced attorney become valuable.
Of course, this answer does not create an attorney client relationship and you should seek the assistance of a competent attorney to help you with this matter. The information presented is for general educational purposes only and there may be facts not disclosed which would call for a different answer.