I had to say goodbye to my long term friend and hunting partner earrlier this year he was 13 and a half, I couldn’t never do it myself so a trip to the vet it was. I held him in my arms until he had passed and bye f**k I sobbed my heart out, it’s a difficult thing to do let them go. I am sure you will do right by the dog and choose the best way/person to do the job. Poor old dog,