What is Heaven and Hell like? I heard that in Heaven everything is gold and you have your own mansion, and that you aren't hungry anymore. In hell, do you just burn in fire, etc? Also, when it comes time for judgment, is it true that God replays your whole life to you to point out all the bad things you've done?
You have some excellent questions there. Unfortunately, we aren't given a lot of details about heaven and hell.
Jesus said that there were many "mansions" or "rooms" in his Father's house (John 14:2). Whether this means that we will each have our own room, or even our own house, is open to debate. The problem is that any description of heaven is an attempt to put spiritual things into physical terms. It's like the old problem of trying to describe a spiral staircase without using your hands to a primitive tribe that lives in one-room, thatched huts. We really don't have the background to fully understand what heaven is like. We know it will be a place of joy (Matthew 25:21-23) and rest (Hebrews 4:1-11). Many people believe that Revelation, chapters 21 and 22, contains a description of heaven. Others say that is a figurative picture of the church here on earth. Even if it is a description of heaven, it is in terms we can understand, and even then we can't imagine what it is really like. I doubt that it has streets paved with actual gold; that is probably just describing how precious the place is, using human ideas of beauty and value. It is a spiritual realm, because God is spirit, so wouldn't have physical characteristics. There are things we won't feel anymore, and hunger is probably one of them. We won't even have need of marriage (Matthew 22:30). If we won't need such as basic thing as sex, we won't have need of food or our other basic human needs.
Hell is described in, perhaps, more detail than heaven, although even that description is pretty basic. We know that it is a place of eternal punishment (Matthew 25:46). It is described as fire prepared for the devil and his angels (Matthew 25:41). Elsewhere mention is made of fire and sulphur (Revelation 20:10), so there will be a foul smell along with the burning. Several times Jesus described it as "outer darkness, where there shall be weeping and gnashing of teeth" (Matthew 8:12; 22:13; 25:30). To some of us the darkness would be more torture than the burning or the smell. Even these descriptions, though, are probably insufficient to give us the full impact of hell. The most important thing is that hell will be without God. To know that one could have had the glory of God's presence and to be without it would be torment. In addition, being without God it would be a place without love, joy, peace, or any of the fruit of the spirit. Imagine a place where nobody was capable of doing any good and that would be hell.
When I was a child I used to believe that at the judgement a big movie screen would be put up and each person would have all the good and bad things in his life replayed for everyone to see. I no longer believe that. If we could earn our salvation by our good works outweighing our sins that might be a valid picture of judgement. However, we can not earn our salvation, no matter how many good things we do and how few sins we commit. "For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast." (Ephesians 2:8-9) We are saved if we have had our sins washed away. We are lost if we are still in our sins. Therefore, God doesn't need to replay our life. If we have one sin, we are lost. If our sins have been removed by the blood of Jesus the Messiah, we are saved. The picture of the judgement given in Matthew 25 is simply a separation of the "sheep from the goats." Revelation 20:12-15 indicates that the separation will be based on whether one's name is written in the "book of life" or not. No need to view all of the lives of everybody who ever lived; just call out the names of those in the book of life and take them to heaven and the rest to hell. That's a lot more efficient than playing out everybody's life, since we have all sinned anyway. (For more on the book of life go to my article, Zoe's Bible)
I hope I have at least helped answer some of your questions.