1. and 2. Your hosting company should be able to register your domain name for you (or at least you should be able to register the domain at the same time as you subscribe to their hosting package).
This search should give you a few choices of hosting companies.
3. WebmasterWorld? It canīt be that hard to run... :)
Just kidding! Im sure theres a lot of effort behind WW.
If you want to set up your own discussion forum then you can get some free software (Snitz forums are reasonably easy to integrate). It wont be up to the standard of WW, but what do you want for free? :)
To maintain a forum doesnt take that much effort initially, as you will have no members, and as your members do increase, you can appoint moderators to perform certain functions.
All this can be done from a web based admin section and doesnt take any hardcore IT knowledge (thatīs necessary if you want to design your own forum).