MELONI - While reading the Doctrine and Covenants, I came across SECTION 132 which says:

15 Therefore, if a man marry him a wife in the world, and he marry her not by me nor by my word, and he covenant with her so long as he is in the world and she with him, their covenant and marriage are not of force when they are dead, and when they are out of the world; therefore, they are not bound by any law when they are out of the world.
16 Therefore, when they are out of the world they neither marry nor are given in marriage; but are appointed angels in heaven, which angels are ministering servants, to minister for those who are worthy of a far more, and an exceeding, and an eternal weight of glory.
17 For these angels did not abide my law; therefore, they cannot be enlarged, but remain separately and singly, without exaltation, in their saved condition, to all eternity; and from henceforth are not gods, but are angels of God forever and ever. (D&C 132:15-17)

My question to you is that if people are not married or given in marriage when they are out of the world, then how are people able to have sealings performed for them in the temple after their death? Also, what is the purpose of sealing them if they cannot recieve exaltation as stated in verse 17?

On another topic, I was wondering if we will ever have our memory of pre-existence restored. If so, at what point that will happen?

JOEL - One thing to keep in mind is that when the scripture says, "when they are out of the world", it is talking about a time after the resurrection and final judgment. Verse 17 says "they remain separately and singly, without exaltation, in their saved condition", indicating that the scriptures are talking about people who are already saved souls; something that happens after the final judgment.
Jesus also described this in Luke:

"Therefore in the resurrection whose wife of them is she? for seven had her to wife.
And Jesus answering said unto them, The children of this world marry, and are given in marriage:
But they which shall be accounted worthy to obtain that world, and the resurrection from the dead, neither marry, nor are given in marriage:
Neither can they die any more: for they are equal unto the angels; and are the children of God, being the children of the resurrection" (Luke 20:33-36).

And in Mark:
"For when they shall rise from the dead, they neither marry, nor are given in marriage; but are as the angels which are in heaven." (Mark 12:25)

So here they are talking about the condition of a civily married husband and wife after the resurrection which of course hasn't happened yet.
These scriptures are explaining that once one has been resurrected, judged, and assigned a kingdom of glory there is no longer the possibility to be married or sealed to someone and achieve exaltation in the Celestial kingdom, and that the civil marriage they had on earth will no longer be valid. But before the resurrection happens the spirits of all those deceased, who are in Spirit Prison, are being taught the gospel and waiting for us to perform the ordinances for them in our temples. Those who would have accepted the gospel on earth if they had been given a chance to hear it will have the opportunity to accept it in heaven and eventually obtain exaltation(D&C 137: 7-8), provided of course that they accept it and have the required temple ordinances performed before their resurrection.

In regards to our memory of the pre-existance, President George Q. Cannon said:
"You have heard of men who have been drowning or have fallen from a great height describe that in about a second or two every event of their lives passed before them like a panorama with the rapidity of lightning. This shows what power there is latent in the human mind, which, when quickened by the power of God, will make men and women recall not only that which pertains to this life, but our memories will stretch back to the life we had before we came here, with the associations we had with our Father and God and with those bright spirits that stand around His throne and with the righteous and holy ones." (Gospel Truth: Discourses and Writings of President George Q. Cannon, p. 60)