If you're using 100% live rock and sand, you will be fine. To prevent any die-off, bring a cooler or some container you can keep water in and transport your rock that way.
My first tank was a 16 gallon. And, like you, bought live rock from Petco. I didn't want die-off and therefore, transported it wet.
Added caribsea sand and put the tank together. Lo and behold, my live rock came with a hitchiker BTA and 2 emerald crabs.
I tested every single day for the first couple weeks and never saw any measurable ammonia.
Now, as a new reefer, I made many mistakes in the first few months, but that BTA and both emerald crabs are still alive and kicking.
IMO:
The question is not weather the tank is ready for corals.
The question is: Are you ready?
If I were you, I would purchase the rocks, sand, etc, and if they will let you, the torch. Take all but the torch home and get your tank running.
Maybe run it for a week or two and make sure you can maintain temperature, water level, etc, and do a water change to make sure you have a good system down.
Then, go back and get that torch.