If for any reason you are unable to carry out the duties then you need to contact the solicitor handling the estate i think and ask if you can be released from the role.
Nobody is obliged to act as an executor. You can simply decline to do the job. If you do, any reserve executor (named in the will) can do the job. If no other executor was appointed in the will, a close family member can seek probate and become the executor.
However, if you accept the role, you must ensure that the terms of the will are carried out. Willful failure to do so could result in imprisonment.