No problems. 30 minutes is not far. Just request that they wrap the live rock in wet newspaper. You may want to bring your own newspaper, just in case.
Make sure that your tank is ready with water at the proper salinity and temperature. Only fill the tank about 2/3 full to allow for the rock and sand. You should also have an extra 5 gallons of water ready, just in case. This is good advice to follow on a permanent basis.
Add the base rock pieces first, preferably "legs" that you will stack larger flat pieces on top of. Then add the sand, which will create stability around the base rocks. Then finish creating your reef structure. Here is an example:
I'm not saying your structure should look like this, but notice that the large flat rocks are not touching the sand. This allows for great circulation and helps prevent cyno outbreaks and algae blooms.
I would recommend 2 power heads for this tank size. Allow the system to run for a couple of weeks before considering any livestock. This will allow ample time for copepod and amphipod populations to spread. During this time test for ammonia and nitrite.
After about 2 weeks your diatom bloom will hit, at which point you could consider a very small clean up crew (CUC) of 1 or 2 snails and 2 or 3 hermit crabs.
When the diatom hits it is time to start testing for alkalinity and calcium, so have those test kits ready, along with a buffer and calcium supplement, or a 2 part additive such as b-Ionic. I personally use Kent Marine Super Buffer DKH and Kent Marine liquid Calcium Chloride.
By the way, it is possible that after adding your sand the tank will be so cloudy that you can't finish the live rock structure.
If this happens, just place the rock into the 5 gallons of extra water to keep it wet, and finish adding the rock after 24 to 48 hours, when the water is clear.
I personally would have a 7 to 10 gallon storage tote for this purpose, rather than a bucket.
It makes it easier to work with the rock pieces and see what you have available when you are ready to complete the reef. Plus, the rock could live forever inside that tote, so long as you have a powerhead circulating water and keep it at room temperature.