If you don't know how to install it, and can't learn, you won't know how to maintain it long term, and you will have a lot of problems as a result of that.
If it helps paying for the install service, then I would do that. The Cloud version is much more expensive I believe. Once you have it installed and you are the administrator, there is an admin control panel with various settings and you'd need to explore that a bit first and work things out. Mostly though it can pretty much be used out of the box if you keep it simple. But there are things like "permissions" to set for users.
If you find a server you want to use they can also help with installing it, but they won't know how to use the Xenforo software. You can get the domain name bought via the server usually. I would start with the server and domain name.