If God is so good why does he allow so much evil ?
Because He did not make a bunch of robots but gives each person freedom of choice to do good or evil. Jesus told a story about a man who planted good seed in his field:

    Jesus told them another parable: "The kingdom of heaven is like a man who sowed good seed in his field. But while everyone was sleeping, his enemy came and sowed weeds among the wheat, and went away. When the wheat sprouted and formed heads, then the weeds also appeared. "The owner's servants came to him and said, 'Sir, didn't you sow good seed in your field? Where then did the weeds come from?' "'An enemy did this,' he replied. "The servants asked him, 'Do you want us to go and pull them up?' "'No,' he answered, 'because while you are pulling the weeds, you may root up the wheat with them.  Let both grow together until the harvest. At that time I will tell the harvesters: First collect the weeds and tie them in bundles to be burned; then gather the wheat and bring it into my barn.'" Matt 13:24-30 (NIV)

I've lead a fairly good life will go to heaven ?
Good depends on who you compare yourself to. We can always find some better and worse than ourselves, but God's standard is himself, or in other words perfection. Who can stand a chance? The Bible says:
"for all have sinned and fall short of the glory of God," Rom 3:23 (NIV) and
 "For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord." Rom 6:23 (NIV)

How then can I be good enough to  get to Heaven ?
You can't! There is no way you can be good enough to earn your way into heaven. Salvation is a free gift:
 "For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life." John 3:16 (NIV)

How then can I be saved?
Rom 10:9-11 says, "that if you confess with your mouth, "Jesus is Lord," and believe in your heart that God raised him from the dead, you will be saved. For it is with your heart that you believe and are justified, and it is with your mouth that you confess and are saved. As the Scripture says, "Anyone who trusts in him will never be put to shame." (NIV)

Is it true that may roads lead to the same destination? Or that many religions will get us to heaven?
No!
 In John 14:6 Jesus answered, "I am the way and the truth and the life. No one comes to the Father except through me."
The Bible also says:
 "For there is one God and one mediator between God and men, the man Christ Jesus," 1 Tim 2:5 5 (NIV)

So how then do I become a Christian?
It is so simple that it is almost too easy! Confess to God that you're a sinner and that you need his forgiveness. Believe that His death on the Cross and resurrection paid the penalty for our Sins, and ask Jesus to make you Born again, for Jesus said:
 In reply Jesus declared, "I tell you the truth, no one can see the kingdom of God unless he is born again." John 3:3 (NIV)

How do I maintain my relationship with God ?
Get a bible and read it every day. Pray. Find some other believers and join a good Bible Believing church and don't be ashamed to tell others about God's word. But most of all obey. For the Lord says to obey is better than sacrifice
1 Sam 15:22-23 And Samuel said, Hath the LORD as great delight in burnt offerings and sacrifices, as in obeying the voice of the LORD? Behold, to obey is better than sacrifice, and to hearken than the fat of rams. For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry.  (KJV)

After I become a Christian will everything go perfectly and will I get rich ?
No and probably not. Jesus said:

 "Remember the word that I said unto you, The servant is not greater than his lord. If they have persecuted me, they will also persecute you; if they have kept my saying, they will keep yours also." John 15:20 (KJV)

But you will have a peace that will leave most of the world scratching their heads. Jesus said:
 "Peace I leave with you; my peace I give you. I do not give to you as the world gives. Do not let your hearts be troubled and do not be afraid." John 14:27 (NIV)
 He also said, "I have told you these things, so that in me you may have peace. In this world you will have trouble. But take heart! I have overcome the world." John 16:33 (NIV)

The bible also says:
 "May the God of hope fill you with all joy and peace as you trust in him, so that you may overflow with hope by the power of the Holy Spirit." Rom 15:13 (NIV) "And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus." Phil 4:7 (NIV)

Can I become a Christian, so that I can get into heaven, and then live my life the same way as I always have?
You probably could. There are a lot of people who do that. But I believe they are some of the most miserable people on the planet. It is not fun living a double life. Jesus said:

"No servant can serve two masters. Either he will hate the one and love the other, or he will be devoted to the one and despise the other. You cannot serve both God and Money."
Luke 16:13 (NIV) and
"So, because you are lukewarm-- neither hot nor cold-- I am about to spit you out of my mouth." Rev 3:16 (NIV)

And why would you want to. You cannot do better for yourself than what the Lord would desire for you. Jesus said:
"Ask and it will be given to you; seek and you will find; knock and the door will be opened to you. For everyone who asks receives; he who seeks finds; and to him who knocks, the door will be opened. "Which of you, if his son asks for bread, will give him a stone? Or if he asks for a fish, will give him a snake? If you, then, though you are evil, know how to give good gifts to your children, how much more will your Father in heaven give good gifts to those who ask him! Matt 7:7-11 (NIV)
Do not take my word for any of this but get a Bible for yourself and look up these verses.