Is it possible for a man to change another man's heart?

Sure. Counsellors do so frequently.

It is possible but someone has to want to change.

Many transplant surgeries prove it is so.

Yes. Literally so and figuratively as well. 

Yes. Dr. Christiaan Barnard with his team, performed the world's first human-to-human heart transplant operation on 3 December 1967.

The decision to change is an individual's Spiritual choice. Another man may lead one to that point, but they can't make another change their heart.

No. Jesus washes us of all sin, then we are baptized with the Holy Spirit and, born again the Holy Spirit transforms the heart from indifference and hostility toward God to a love of God and a desire for righteousness and holiness. Flesh gives birth to flesh, but the Spirit gives birth to spirit. 

Fix, alter, change or replace, all thanks to the wonders of modern medicine.

Yes, it is possible.

Yes, absolutely.  It happens all the time.   Not only is it possible for a man AND a woman to change another man OR woman's heart, but they do it all the time with great succes.

I know because I am the financial analyst for the heart transplant program at a Top 10 teaching hospital.