This link describes F1 gearboxes.
I don't think the transmission for sale on eBay is remotely connected to an F1 transmission. They are incredibly expensive, rare, and unobtainable. They need complex electonics and hydraulics to run them, and they operate in a manner that really isn't applicable to a transmission used on a "normal" road vehicle. Additionally, many parts inside one of the F1 transmissions are designed for just a few hours, and then need to be replaced.
The only step down transmissions I know of are industrial and agricultural. Definitely, without any doubt, nothing to do with F1