I will lose at least 10 coins at the withdrawal from the Yobit Exchange at the exchange commission and this is excluding gas for transfer to exchange. This is not very good news.
Coinvest is still in negotiation with exchanges considering their part in this process.
Is there the need to swap again, mine is in the MEW only. But its good that you found out about that security issue now than it will be in the next years when price is already up. I may have misunderstood it but it says "THE TOKEN UPGRADE CAN ONLY OCCUR USING THE COINVEST WALLET".
Does it mean I will have to install the coinvest wallet to upgrade my coins?
Coinvest is online wallet pretty much like MEW, but it will allow you to upgrade your COIN tokens automatically, without unnecessary frictions. You can use private key of your current wallet address where you store your COINs or transfer them to another address, which you will use to upgrade tokens.