Glad to hear you control the domain name – that’s important!
To transfer the content, you’d probably have to copy one page at a time from OSP then paste into WordPress pages. But it might be worth finding out (from OSP) whether there’s a way to export the content in one go, ready to import into WordPress (probably not but it’s worth asking).
I can see it would be a complete redesign. Here’s a suggested roadmap:
1) Buy hosting. There are plenty of reputable companies out there that do good, inexpensive WordPress hosting.
2) Install WordPress. Some hosts install it for you or have a one-click installation tool.
3) Choose and install a theme: it could be a free or premium theme that you customise with your own branding; or you could pay a developer to build one to your specific needs. Before you do anything, write a brief so you’re certain about what you want.
4) If you need extra functionality – such as a calendar – you’ll need to install plugins or use some third party code.
5) When you’re ready to launch, change the domain’s DNS settings so it points to the hosting. This bit is simple if you’ve done it before, confusing if you haven’t.
6) There are a few post-launch tasks and checks you can do to ensure that Google and other search engines notice the changes quickly.
How much of this you’d be able to do yourselves and whether you’ll need to hire someone to help or find volunteer assistance, depends on your own skills and time/willingness to learn, and how much customisation you need to do to the theme.
These forums are for help with the self-hosted WordPress but it would be remiss of me not to mention the hosted-for-you version, which is WordPress.com. It’s less flexible but a good bet for simpler websites, provided you can find a theme that meets your needs.
