A preventive health program is important, and unless you've talked directly with the seller I would not count on anything said at the salebarn.
Our vet used to say let them rest 1 hour for every hour on the truck - we usually work them the next morning after they have been eaten.
The biggest thing we have found is how much it's worth to fill a pen on the same day.  Bringing in cattle over a period of time is an invitation for disaster, and even if they don't get clinically sick they will not perform as well pay weight to pay weight, most likely because of sub clinical sickness going on in the mixed together group.