It's hard to answer your questions for all of the churches of Christ, as we have no governing body/counsel/home office/headquarters/creed/etc. Each congregation is autonomous, our elders lead each congregation separately. That's not to say we aren't in fellowship with each other or that we ignore each other, but some (many if you really get down to it) believe different things on different subjects. Most of which are not salvational issues. You would really have to sit down and talk with the the elders or the minster at your local congregation to get the answers you're looking for.
Having said that, I can do my best to answer you from what I know of being a member of a church of Christ.
In general, we are not premillennial. There some who hold this belief, some people out there may not accept them. You may never be asked to lead or teach, but again, it's up to the individual congregations. I do know in one congregation I worshipped with for a few years (military, moved around a good bit) there was a man who was a premillennialist and was very vocal about it, almost to a point of asking him to leave, not out of dislike but because it wasn't the teaching of that congregation. But he was still welcomed to worship.
I had to look up replacement theology, never heard of it before. But that, along with a belief in Zionism, likely won't be found. In the OT/Judaism/Old Law, the place of worship was important. The tabernacle and later the temple, Jerusalem being a holy place. But the kingdom of God as we understand it to be, is not a place/nation/building/race of people, but the people who believe and have been baptized into Christ. Salvation or God's chosen are no longer tied to a specific race of people or a specific location or nation. Again, you should not be shunned from worship, but asked not to teach the things that are considered to be in error. It would likely be seen as divisive.
Having said that, we love the Old Testament! The entire thing points to Jesus! There are so many amazing lessons to be drawn from it, but we don't accept it as binding anymore. Like Paul said, it is a school master or a tutor, to lead us to the Christ/Messiah. (Galatians 3:23-29 speaks to this, as well as replacement theology/Zionism.)
Baptism being a necessary part of salvation will most certainly be a universal belief of the churches of Christ. Again, the elders of the congregation will lead in the way they will lead. I can't tell you if they will accept your baptism as an outward show of your prior salvation (if that is your belief and have been baptized in that manner). But, its very likely the elders/minister will want to study with you to fully understand your stances before any decision is made. And its likely you will be asked if you want to be baptized for salvation. But if you choose not to be, or feel like you are already saved, I see no rational eldership asking you not to worship with the congregation. You may not be considered a member of the congregation or be a leader/teacher, but always welcome to worship.
Now that my book of an answer is coming to a close, I have always been a part of congregations of the churches of Christ that are super loving. I have seen tough decisions made by elderships, but it tears them apart having to make those kinds of decisions. I know there are congregations out there that are sour and ultra conservative to a point of exclusion, but I don't feel that's the church that Jesus is the head of.
And I'm done. I hope this helped a bit. Even though its a few months after you asked about it.
