I have an existing forum with many posts. Is there an easy way to change the forum name to something else? I assume the data folder under forums would need to be renamed but not sure what else.

You cannot change the topic name due to a pre-existing post located there, but if you want to change that.
1. data/forum edit name=>"{forum_name_here}"
2. data/topic edit forum=>"{forum_name_here}"

That's the best way of doing it since it's not saving inside a database so you would have to manually update it all.