At the moment of the fork a copy of the BTC blockchain will be created and the two coins up to that point will have the exact same ledger. After that, each will record their transactions on their respective, separate blockchains, so the blockchains will start differentiating. So when you make a transaction after the fork, let's say with BTC, that will be recorded only on the BTC blockchain, not on the BTG blockchain. So your BTGs aren't affected. Or at least they shouldn't be, if the coin is indeed protected from replay attacks.

Now, on the copied blockchain exists the same number of coins as the original, since it's an exact copy, distributed in the same way. But instead of being called BTC they are now called BTG and are mined differently from that point on. So if you have BTC at the time of the fork, as recorded on the Bitcoin blockchain, you automatically have BTG on the new blockchain and just have to follow the procedure to claim them. At least that's how I understand it. I could be wrong though. Like I said I'm a newbie too! :)

As far as the selling goes, well you're right that no one can accurately predict what's going to happen. Maybe it's safer to wait and see since you are not in the game already. After all the loss of not having BTG won't be big I think. Like I said it's predicted to come out at about 5% of BTC.

And I agree with you that it's a nice concept, the re-decentralization of the mining. I just don't think their motives are that pure and thus they won't be able to persuade the people and back the new coin.

Anyway, only time will tell. Till then... Happy Steeming!