I just ordered a C3000, here's what I got from this forum alone that should answer our questions:
The USB host port on the C3000 isn't On-The-Go; it is a fully function USB 1.1 interface port supported by the PX270 processor onboard. See the specifications for that processor for more details, but basically OTG is a Samsung creation for its ARM-architecture (same as PXA series) processors. From what I understood, OTG is unpowered (except for data pins of course), but still a USB host. Simply put, the port on the C3000 should be the exact same port on the SL-6000.
The cable, therefore, used is discussed in the SL-6000 forums, and the drivers for the SL-6000 should of course work for the C3000. It's a Mini-USB Type A Female, and you need a Mini Type-A Male to Type A (full sized) Female cable. All the details are in the SL-6000 forum. Sorry I can't provide a link (can't find the specific post!) but it's there.
The C3000 shouldn't have a dedicated graphics chip, but those chips never did much except help one program, specifically designed to use them, render movies or the like. If we look at the Toshiba E705 series, which had the chip (Imageon 100), the Toshiba had (as far as I remember) a special $20 VGA-out attachment and a fast video renderer. Aside from that, nothing was gained.