How to upload a custom NewForm.aspx to list and set it as default newform using PowerShell?

Hi,

I have a custom NewForm (sitting on my drive as aspx-file exported from SharePoint Designer) and I need to - using PowerShell - upload this file to the rootfolder of the list and set this aspx-file as the default newform for this list.

To avoid any confusion as to why I need to do this:
I'm working on a version 2 of a SharePoint site, where the provisioning of the whole new site is done using PowerShell. A couple of the newforms in the old solution are customized and I need to reuse them on the new site. So, to be able to provision the whole thing with PowerShell.

Can anybody help me out here? Cmdlet/script/command to upload a physical aspx-file from a drive to the rootfolder of a list and set this file as the default newform...

Thanks!