The spell is in the PHB, and read as fallows.
“Magic Weapon: gives a weapon a +1 enhancement bonus to attack and damage rolls. If you’re a good cleric, the cleric of a good deity, or a paladin, the weapon is considered blessed, which means it has special effects on certain creatures. You can’t cast this spell on a natural weapon such as an unarmed strike.”
1. Does this +1 stack with, let’s say, a +2 magic weapon, making it a total of +3?
2. What are the benefits of the bless part of this spell?
3. If the answer to question 1 is "no", can you still use this spell to get the benefits of the bless part?
“Magic Weapon: gives a weapon a +1 enhancement bonus to attack and damage rolls. If you’re a good cleric, the cleric of a good deity, or a paladin, the weapon is considered blessed, which means it has special effects on certain creatures. You can’t cast this spell on a natural weapon such as an unarmed strike.”
1. Does this +1 stack with, let’s say, a +2 magic weapon, making it a total of +3?
2. What are the benefits of the bless part of this spell?
3. If the answer to question 1 is "no", can you still use this spell to get the benefits of the bless part?