If there are no instructions there specifically for your tablet, try some of the methods for other tablets. One of them will probably work and you won't hurt anything by trying.
As for stock ROMs for Coby devices, there aren't any from Coby and there never will be. Coby has been out of business for a few years now. There are also no system dumps for your device, which means no way to restore your tablet, with the possible exception of a factory reset.
Your device is likely one of the later units Coby released with a nand lock on it. Installing a custom recovery or custom ROM will trip the nand lock and render the internal storage useless. Try a custom ROM since you have little to lose anyway, but be aware of the possible outcome.