You can get everything set up all at once.
I would wait a few days after adjusting everything to try to feed, but it's really up to you. I personally would wait, it's not going to hurt him. If you offer now he may or may not eat, no biggie.
As for a seperate feeding tub, that is old school and proven counter productive. I have always fed inside their enclosures and have never been bitten or even struck at within the enclosure.
This topic always brings a little debate, but you'll find the vast majority feed inside the enclosure. Using a feeding tub increases the chance of a regurge as well as increases the chance of getting tagged while the snake is in feed mode. Also, it can stress the snake prior to it even eating and cause refusals.