First, what form do you take when you go to heaven. If you died at age 40, do you take that form or the form when you were 20? Also, my friend told me there are different parts in Heaven. There's a part where people who can enjoy a very good life, normal, or just OK. Is this true or is it totally equal?
I will try to answer your questions, although in some cases the answer may be, "I don't know for sure."
What form will we take in heaven? Paul says it will be a spiritual body. Read 1 Corinthians 15: 35-58. The new body will not be like our old body, so we can't say whether it will show age like our old body. A similar question to yours would be, "what if I lost a leg, or an arm?" The new body would have no relation to the handicaps of the old body, just as a flower is different in form from the seed, and may grow just as beautiful if the seed had been scratched on the outside.
We are not given a thorough description of heaven, so nobody can know whether there are different parts of heaven. Since it will be inhabited by spiritual beings that are free from the cares and concerns of this life, I suspect that it will be very much the same for everybody, but I don't know. The principal feature of heaven, that which will occupy our thoughts and actions, appears to be the tangible presence of God. This in itself will be so overwhelmingly glorious to us that all else won't matter. Heaven will probably be so much different from anything we can imagine that human words can not describe it. If chapters 21 and 22 of the Revelation are descriptions of heaven, then they are just describing it in limited human terms and should not be taken as literally exact.