Is part of the kingdom gospel "repent and be baptized for remission of sins"? Of course it is. Now, what if a man said he was sent to preach the gospel, but he was not sent to baptize. Which gospel could he possibly be referring to? The kingdom gospel says "repent and be baptized for remission of sins". Either he is a charlatan, preaching a charlatan gospel, or his gospel does NOT contain "repent and be baptized for remission of sins." And what if that man said that God is going to judge the secrets of men by his gospel one day? Either he is a charlatan or God isn't requiring "repent and be baptized for remission of sins" now.
He calls his gospel "The Gospel of the Grace of God." It's different. Different name, different time, different people. And God told him that his gospel WILL be used to judge men one day. (ROm. 2:16).
Do you still think that water baptism is for today?
The one the the same gospel. The reference to "gospel" here is of course, to the entire doctrine of Christ, whether expressed in the gospels, or the epistles, or, -- at least as we Catholics understand it, -- in the continuing teaching of the living Church. So, the gospel has a call to conversion and baptism, but it is not its entire content. There is also call to learning, to virtue, to sanctity, -- all these are preached to the baptized. So it is entirely possible to preach the gospel to people already converted to Catholicism, -- our priests do it at every Mass, and in fact, Protestant ministers also preach primarily to the congregation that is already baptized. St. Paul also said something similar, and a look at his letters show depth of content specifically for people who are already committed Christians. So I don't understand your premise that "repent and be baptized for remission of sins" cannot be a part of the same one gospel.
Do you still think that water baptism is for today?
Of course. Christ's command is for all times: the life in His Church begins at baptism. At the entrance of a church there is a cup of holy water, or often an entire baptismal pool. When you enter the church and when you exit it you dip your fingers in the water and cross yourself. That is a reminder of the sweet water of baptism that made you a Catholic man, called to be saint.