Studio software/hardware from Pinnacle Systems will let you capture an analogue source into digital format from your DV camcorder. I have Studio DV Plus, which is a capture card with two Firewire ports, and it comes with Studio software.
Note that this ONLY captures digital sources. What you need is a camcorder that can take accept an analogue source and do a "passthrough" conversion in the camera, and send the now digital source via Firewire to the capture card. You have to make sure that your camcorder can do passthrough conversion.
My Sony PC100E, for example, has analogue inputs BUT it can't do passthrough conversion. Of course, I can tape the analogue input onto the DV tape and then capture that via Firewire, but for some reason known only to Sony it can't simply pass the converted signal via Firewire; it can only tape the analogue signal first. (There are several Sony camcorders which can, and apparently it is only a firmware issue with supposedly the only fix being some form of hack.)
With passthrough capability, the process is only electronic, as you say. If the salesman doesn't know about this, I'd suggest asking to take a look at the manual.
Alternatively, I think there are other Pinnacle products (and perhaps Canopus products) which let you capture analogue directly - but I don't know whether they convert into DV format.
But note that this only addresses the issue of capturing. Certainly with the Studio software you can't do viewing of live TV or timeshifting. There's a preview box while you capture, but I don't believe it can be scaled to fullscreen.