1. As far as I know at the end of the bible it stated "this is the word of God and whomsoever touches this shall suffer..." or something like that. Why did they change the wording of the Bible?
2.What would you say is the best Bible to study?
The passage you refer to is probably Revelation 22:18-19. "For I testify unto every man that heareth the words of the prophecy of this book, If any man shall add unto these things, God shall add unto him the plagues that are written in this book: And if any man shall take away from the words of the book of this prophecy, God shall take away his part out of the book of life, and out of the holy city, and from the things which are written in this book."
That passage says that it is specifically referring to the prophecies of the book of Revelation. However, the principle does apply to the scripture as a whole. Anything that can not be demonstrated as having been directly inspired by the Holy Spirit should be rejected. And the scripture seems to indicate that the Spirit ended his work of inspiring new scriptures in the first or early second centuries. (See my answer at What Does the Bible Say About..Speaking in Tongues?.)
You asked, "why did they change the wording of the bible?" I would need to know who you think changed the wording of the Bible, and where you think they changed it. I can say that some people translate or paraphrase the Bible in such a way that supports their pet doctrines. These people are not honest translators, and should be held accountable for those places where they mistranslate. But mistranslating the Bible is not changing the original wording. I would have to have examples in order to answer your question fully.
Your second question was which Bible I would say was the best to study. I think the best one is the one that is easiest for you to understand, with some qualifications. I do not usually recommend translations made by one person or a group that might be trying to defend their own beliefs. Thus I would stay away from those with an individual's name on them. I would also be careful about using the New American Version, and especially the Good News Bible. For a different reason I often do not recommend the King James Version; besides several mistranslations, the English is outdated and may be hard to understand. (I quote from the King James Version in my answers because it is not under copyright.) I would also avoid anything that calls itself a paraphrase (The Living Bible) or a condensation (the Readers Digest Bible), because they are admitting that they are not translations.
According to most scholars I have studied, the best English translations are the American Standard Version, the New American Standard Version, and possibly the New International Version. For some people I would recommend the International Children's Bible, because it is written in simple English.
The best recommendation I could make, though, would be to study from two or more translations. The more versions you use, the more different insights you may receive. You will also see where some translators put in their own opinion, because it will be significantly different than other translations.
The example I would like to use is for me the most memorable one. In Luke 17:21 it reads something like this.
"The priests asked Jesus when the kingdom of God will come and he answered that the kingdom of God is not above among the stars and will not come with any visible signs because the Kingdome of God is IN us." This was the earlier translation I read. It could have been the King James Version but I cannot be sure. The later version was a newer translation and said, "...the kingdom of God is WITH us."
Now for me there is a big difference between IN and WITH. Could you explain this for me.
This may or may not be an example of translating a passage to fit the translator's own doctrines. The word used in Luke 17:21 in the Greek has the meaning "within, in the midst or middle." Most versions I consulted used either "within" (8 versions), "among" (4 versions), or "in your midst" (3 versions). One version each used "with" (Current English Version), "in" (New Life Translation), and "inside" (Worldwide English Version), all of which are incorrect translations, although "in" is closer to "within" than the others are. Those that use "among" are really stretching the meaning of the word, too.
There certainly is a difference in idea between "with" and "in" or "within." Jesus was saying that the kingdom is a spiritual rather than physical kingdom. It is not something that is external to (with) a person, but internal (within). The kingdom, which is the church (see What Does the Bible Say About..The Kingdom?), consists of a group of people who are tied together not by nationality or location but by having a common Spirit.
This is also one example of why I say it is good to use several versions to study from. If you read this passage in multiple versions, most would have it correct. You would then suspect that the one that was different might not be accurate.