When someone converts to Christianity and is "reborn in Christ," is it the body or the soul that is reborn, or both? I understand this question can be approached from different denominational positions, depending on how one interprets John 3:3-5.

Jesus replied, &quot;Very truly I tell you, no one can see the kingdom of
God unless they are born again.&quot; &quot;How can someone be born when they
are old?&quot; Nicodemus asked. &quot;Surely they cannot enter a second time
into their mother's womb to be born!&quot; Jesus answered, &quot;Very truly I
tell you, no one can enter the kingdom of God unless they are born of
water and the Spirit.&quot;
— Gospel of John, chapter 3, verses 3–5, NIV
As asked, your question will receive many answers, most of them will be personal opinions. I will not undertake to answer your question as asked.
I will however, give you the scriptures concerning this subject as I know them. You may use them for your research in seeking truth. I also would like to suggest that you seek consultation with your Pastor or other trusted Christian.
Those Scriptures from the King James  version are as follows:

Matthew 11:28  Come unto me, all ye that labour and are heavy laden, and I will give you rest.


Matthew  11:29  Take my yoke upon you, and learn of me; for I am meek and lowly in heart: and ye shall find rest unto your souls.


Matthew 10:28  And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell.


Matthew  16:25  For whosoever will save his life shall lose it: and whosoever will lose his life for my sake shall find it.


Matthew _7:21  Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.


Matthew _7:24  Therefore whosoever heareth these sayings of mine, and doeth them, I will liken him unto a wise man, which built his house upon a rock:


Matthew_7:26  And every one that heareth these sayings of mine, and doeth them not, shall be likened unto a foolish man, which built his house upon the sand:


John_15:15  Henceforth I call you not servants; for the servant knoweth not what his lord doeth: but I have called you friends; for all things that I have heard of my Father I have made known unto you.


Matthew  7:16  Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles?


Matthew  7:17  Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit.


Matthew  7:18  A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit.


Matthew  7:19  Every tree that bringeth not forth good fruit is hewn down, and cast into the fire.


Matthew  7:20  Wherefore by their fruits ye shall know them.

You will also find that some good commentaries will help in understanding not only these, but any other Scriptures.
There are several Bible study aids available for free downloads on the internet, I have found them very helpful. Two fine ones that I use are e-sword and the Word. Both are free and have the ability to download many Bible versions, commentaries, and many other useful things such as maps, and etc.
Good luck in your studies, they are invaluable to new Christians as well as elder Christians.