1. That Jesus took this step of choosing the twelve very seriously can be seen in the fact that he spent the night in prayer. One might wonder why God would pray to Himself but he is one person in three who are the One God. These persons must have a relationship, and their love for one and other is an example of relationship. Also, Jesus in his human nature can indeed want, need and seek the help of the Divine. Finally, he is our model, the example of how we are to live and relate to God. Therefore, when we face any serious decision, or even any decision, we can and should talk to Him about it. We do not know all things; He does. We are not fully wise; He is. It is a fool who does not seek help. Cf. Proverbs 18:15.
2. Not all the names are the same. This may mean that some of the twelve were not prominent in the early church or in the region outside of Palestine. It may be that many of the twelve did not travel after the resurrection but formed a group of eye witnesses in Palestine who could be consulted on what Jesus said and did. However, by the time the gospels were written, the memory of some of them was fading.
3. You will notice that Judas Iscariot is included in the twelve and therefore was empowered to preach, heal and expel demons. However, because he betrayed Christ some might wonder if he really did have this authority and what effect the betrayal might have had. Yes he did have the authority. Nothing in the text indicates anything else. What effect did the betrayal have? None.
This is reminiscent of the question some have when a priest who has ministered for many years is discovered to have been sinful, or he leaves ministry. The doctrine involved is ex opere operato. A validly ordained priest who performs the sacraments properly does truly perform them by God's action and through the ministry of the Church itself without regard to the state of his soul or his eventual status in the priesthood. A priest can return to the lay state voluntarily, with permission, or can have his "license", i.e. the permission to function as a priest, removed by his bishop, but he remains a priest. The sacramental character conferred by ordination is permanent just as baptism is permanent.