HI
are you sure its a Valve lifter?? an exhaust manifold leak at the head will make the same sound as a lifter and well go away as the car warms up
You can take a piece of hose and put one end to your ear and move the other end around the motor to locate the source of the sound.
If it is a lifter the motor well have to come apart to replace a lifter. Head and intake well have to come off.
Good luck
tim