I am not a lawyer, but I did stay at a Holiday Inn Express last night . . . .
As long as the gun is not rendered unsafe and passes all safety and performance functions, there should be no room for any liability.
Attorneys will pursue any avenue for a win regardless of whether it is factual or not. If you were to use your gun in a situation that had a high probability of you being charged with anything, other than justifiable homicide, then there might be a possibility of jury having issues with a "trigger job". In a defense shooting where you are likely too be, or would be found, not guilty or never charged they would likely not even know it had been modified.
Still, even without a "trigger modification" there would be other reasons, plausible or not, that the prosecution would try to hang on you just to win their case.
Get a professional job done, use quality factory made ammo for defensive carry and follow all rules of proper self defenseive measures according to your local laws.