You have a +1 bonus to attack and damage rolls made with this magic weapon.
Proficiency with a longbow allows you to add your proficiency bonus to the attack roll for any attack you make with it.
Notes: Bonus: Magic, Damage, Combat, Ammunition, Heavy, Range, Two-Handed
How much would this cost
Since it’s an uncommon magic item, 500gp may be pretty sufficient for it.
I know that I’ve read somewhere that regular arrows used with a magical bow are counted as magical attacks for the purposes of resistances and immunities but I can’t figure out where I read that. Anyone have a citation for me?
UPDATE: Nevermind. Found it here