So I'd like to change token decimals and token name in a specific contract. Is it possible?
No, you can't (unless they were programmed to allow such change, which would not comply at all with the ERC20 specifications, and as @Zenos Pavlakou mentioned, being able to modify the decimals would defeat the purpose of smart contracts).
What you could do, which would require quite some work, depending the status of the ICO, is issuing a new token with a new name and decimals and allow your current token holders to exchange them for the new one at the corresponding rate so they keep holding the same value. Not easy at all, but doable if you don't have any other alternatives.