There is a copy of Live & Love on the 4th floor of Faneuil Hall sitting on a table next to a sofa.
If the USS Constitution has landed on the top floor of the building, the quest may get bugged and cannot be completed, in the view that the roof had been altered. The quest may still be completed however by asking a companion to dig up the grave instead.
If the USS Constitution has landed on the top floor of the adjacent building and one has triggered the fast travel point at the USS Constitution's new location, the quest may be done without going through Faneuil Hall by simply fast traveling to the ship and jumping off the port bow to get to the roof.
It is not necessary to complete Unlikely Valentine and get the Detective Case Files from Nick's office to start this mission. The quest can also be started by directly going on the roof of the Faneuil Hall building. Unlikely Valentine is only a prerequisite for access to Marty Bullfinch's holotape, not the mission itself.