Hi James,
First, for the forum software Invision is a good choice. I'm a big fan of PHP so you might also want to take a look at what
phpBB has to offer, both are free.
As for the hosting, make sure that the service provides enough bandwidth and web space. If the forum has enough members it can end up using a lot of bandwidth which may be a problem. If you looking for a hosting company, I highly recommend
Hosting Matters for their great service and support.
And finally, the best place to register a domain is definitely with
GoDaddy, their service is great and they are highly recommended everywhere. I would consider something more catchy for the name, like "accountinghelp.com" or similar. Try to avoid making it look like a screen name and make it easy to remember.
Hope this helps.