Missing the concept. Issue a wholly-new gold "dollar" in coin and certificates and let them exchange with now-discontinued federal reserve notes in a free market. If you want "new dollars," buy gold, submit it to the Treasury, and receive back coin or convertible certificates. (This used to be possible.) It's just another currency. Eventually, all the old fiat currency will have been used to purchase gold on the open market (at increasing prices, so better get to the conversion soon).

Oh, yes. By law, allow the public to opt for being paid wages in old dollars or new gold dollars. Eventually, the gold currency will drive out the paper currency according to how fast the public wants to make the change.

I'm not too worried about "trillions" of dollars disastrously vanishing. Will workers vanish? Will factories vanish? Will resources vanish? No. All that will remain. Billions of stock valuation can vanish in a market adjustment, but we don't see any sudden disappearances of goods or services or assets.

The trick is to start from the gold itself. Let people buy the gold with whatever currency they like, then exchange it for coin or certificates. Let the free market settle the exchange rate between gold and fiat dollars by the pricing mechanism. Keep the government out of that. Similarly, let goods and services have a price in fiat dollars and a price in gold dollars, and let the market sort out which currency will be in preference. Put on this basis, people will rapidly figure out how they want to go.