Does being pantheist mean believing in God?
Yes and no. Merriam Webster defines "pantheism" as:
1: a doctrine that equates God with the forces and laws of the universe
2 : the worship of all gods of different creeds, cults, or peoples indifferently; also : toleration of worship of all gods (as at certain periods of the Roman empire) [merriam-webster.com]
The first does not see "god" as separate from the universe.
The second is the acknowledgement that all gods are "god."
Which do you mean?
And then, there is panentheism, which is different from both of the above.
It depends on what you call god---to believe that all things are connected, every living thing is a part of the whole , that every action has a reaction is not the same as believing in a divine being that is seperate from everything else. Sin isn't an issue in panteisim nor is heaven and hell. It is being aware of the consequences of actions and taking responsibility for them
The conception of what is meant by god, is very different in pantheism. God as Nature is entirely immanent and always in process. Since nature only exposes it self in its diversity, I take it that the pantheist god is a plurality which is in the process of realizing itself (more the way William James saw pantheism) it is not a deity.