Does a weapon that is enchanted with the ability to cast a spell that is a concentration spell, require concentration from the user to maintain?
Yes, the user must maintain concentration. The DMG says this about items that cast spells (on page 141):
The spell uses its normal casting time, range, and duration, and the user of the item must concentrate if the spell requires concentration.
Yes, but some items give spell like effects without requiring concentration. See Do magic item spells require concentration?