Hey @Beemerang, reading through this thread I think the only way will be to create the site from scratch in RapidWeaver.
You have a PSD file with a nice looking site-layout, ok. But RapidWeaver relies on premade themes (templates) to work with and so you would have to look for a theme which matches the layout of your psd-file. Since you unlikely will find such a theme, the best way would be to choose one of the freeform-layout themes available for RapidWeaver, for example “Foundation” from Joe Workman, “Foundry” from elixir graphics for “UIkit” from WeaversKingdom:
With these “themes” you can build your own layouts (in most cases very close to the one that you need) and don’t depend on the layout of some premade theme. By the way: you absolutely need the Stacks plugin from YourHead to use these solutions.
Then you can export the parts of your psd-layout which you need for your site (backgrounds and other graphics) and or pick the color values from the psd and use them with the Foundation/Foundry/Uikit stacks to build a site that comes as near as possible to your psd-layout. That said, there is definitely no way to “convert” or export a psd-file to be automatically used as a theme in RapidWeaver. There will always be a lot of manual work to get the look that you achieve. But the way I described is the best to achieve a similar result as in some psd-layout…