"Soldiers Died" lists John Guerins as born in Cappoquin, but residing in Dungarvan: 5189 Private John Guerins died at home 23rd March 1915. ** However, you state he is buried in Tralee (have you seen his headstone?) and 'at home' may mean in the depot though usually when they write ' at home' it means the homeplace. I have to leave that one up to you to decide.
In the 1911 Census Returns, there is listed as living at 12 Strand Street, Dungarvan:
Guerin - John and Bridget, Denis.
This seems to be your John.
**Waterford County Council has computerised the Death Registers of the area, so they may provide you with more information.
Good luck.