I want to make some python scripts to create an "Appliance" with VirtualBox. However, I can't find any documentation anywhere on making calls to VBoxService.exe. Well, I've found stuff that works from OUTSIDE the Machine, but nothing from working from inside the machine.
Does anyone know anything about this? If there's a library for another language like C I'd be okay with it, though Python would be heavily preferred.
Consider using libvirt. The VirtualBox support is bleeding-edge (not in any release, may not even be in source control yet, but is available as a set of patches on the mailing list) -- but this single API, available for C, Python and several other languages, lets you control virtual machines and images running in Qemu/KVM, Xen, LXC (Linux Containers), UML (User-Mode Linux), OpenVZ and others.
I build and administer virtual appliances (in an automated QA context) using libvirt with the qemu/KVM backend, and it meets my needs very well.
libvirt can be configured to allow remote access (such as controlling or querying VBoxService or libvirtd from within one of the VMs, which you appear to want to do -- though I question the wisdom and utility), with numerous authentication and transport options available.
[Caveat: libvirt principally targets Unixlike operating systems; it can be built for win32, but YMMV]