Re: answers always bring more questions

"i would like to know how positive you are of these things"

These "things" cannot be sluffed-off and replaced with our own ideas.  They are written in the Word of God as "Thus Sayeth the Lord". If He said it, that makes it truth (reality).  Personally, I believe in the infalable and literal Word of God.  Whatever He says is Truth, therefore I have to go against my own way of thinking and align with the mind of Christ.  "My thoughts are not your thoughts, and my ways are not you ways" Isa 55:8, but He gave us His thoughts in His Word and in His Son (The Word)who became flesh, and we can know His thoughts and ways.  He also gave us (believers) The Holy Spirit who illuminates us in the Word and points us to Christ.  We cannot pick and choose what parts of The Bible we want to believe and reject the other parts. You may have heard of the Thomas Jefferson version of the Bible, he cut out all the parts he didn't believe and taught this edited version to his childern.  But we must believe every jot and tittle or we will never understand the full consel of God.  This cannot be done in human strength, it must be done in (by)The Holy Spirit.  So the answer to this question is:  it all depends on how much faith you have in what God says.  My belief or unbelief doesn't change the truth of The Word of God one iota, It is true wether I believe it or not.

"if we are a new creation, then what is different about us?"

He says we are partakers of His Divine Nature, I accept this by faith because He said so.  We are born again and given The Holy Spirit, which makes us different form the natural man, He makes us a new Creation.  From Divine viewpoint God sees two types of humanity, the unsaved (natural man)who is dead in His sins and the saved (those He placed in union with Christ), but there also are two groups of belivers.  There are the spiritual man (those growing in Grace and Knowledge of our Lord Jesus Christ 2Pet 3:18) and the carnal man (those who are save and reject a daily intake of Bible Doctrine as there No. 1 priorty in  life, whose thoughts and action are similar to the natural man (unbeliever).  By sight you cannot tell the apart, but they are saved and will go to heaven when they die because at some point in thier life they belived "that Jesus is the Christ, the Son of God".  1Co 3:1  And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, [even] as unto babes in Christ. As you can see from this verse Paul could not communicate spiritual truths to the Corinthians, he could only speak to them in baby talk because they were acting like natural men.  We cannot look at he  outward appearance of someone, it's God who looks upon the heart.  But even in the back of the carnal man's mind is the Holy Spirit at work convicting and prodding them on in the spiritual life.

"how do we go about being changed into his image?"

We exercise faith in God that He is going to do it, He has predestined it. Rom 8:29  For those whom He foreknew, He also predestined to become conformed to the image of His Son, so that He would be the firstborn among many brethren;
The Father promises He will do this, and it will happen because He says it will.  I can go the easy way by trusting Him or I can do it the hard way by trying to imatate Christ.  We will never be fully conformed to His image until we are raptured and given our glorified bodies, and wht comes next is to spend eternity in His presence learn grace.

"if we are one in christ, does this mean we are god too?"
No, we are joined to the Glorified Humanity of Christ but as He is so are we 1Jo 4:17 ....because as He is, so also are we in this world.

"how is it we are first fruits among his creation when so many came before us? how are we the salt of the earth? the light of the world? the temple of the holy spirit? what is the circumcision not made with human hands? how does this effect us?"
These are too many questions to answer at one sitting.  If you ask one at a time I will be able to give you a more thorough answer.  But the simple answer to all these questions is: God said so in His Word.  We apply faith to His Word. 
Heb 11:6  But without faith [it is] impossible to please [him]: for he that cometh to God must believe that he is, and [that] he is a rewarder of them that diligently seek him.
Joh 7:17  If any man will do his will, he shall know of the doctrine, whether it be of God, or [whether] I speak of myself.