Hi Dave,
What kind of website do you want? The cost will vary based on that. Please provide more info.
Also, here is some info regarding pricing:
Software version
You can decide which version you need based on the features you need; here is a comparison chart:
https://www.ultimatewb.com/compare-uwb
I can also help you decide, if you provide more info.
Web Hosting
This also will depend on the type of website you want. Here's a comparison of the plans:
https://www.ultimatewb.com/domain-names-web-hosting
Domain
The domain you already registered should connect with the UltimateWB web hosting plan without any issue, if it is the standard domain register, like most are, without restrictions of where you use your domain.
Web Design
You can decide to create the website yourself through the admin panel, or we can create it for you. Here are the web design packages: https://www.ultimatewb.com/pro-services#webdesign
Hope this helps!