No, the GOP wants it ended so it will be quick.
They want to replace it with their own plan, which could be as bad or worse. And since they want to repeal and replace rather than just repeal either they repeal now, but delay the effective date until they have their own plan in place, or delay the repeal until they have their plan. Either way Obamacare will be us for a while.
Day one for President Trump is 21 January. 20 January is for ceremonies and getting transition processes signed and sealed.
I hope the finalized law and plan will be ready for signing on his desk by 0800. No executive orders needed.