I can't speak to practices in your locale but in the states a nuc is defined as a smal colony with enough frames to establish a colony. Generally this is a a five frame box containing at least one frame of honey, one frame of pollen and one or more frames of brood with enough bees to cover and a laying queen to get it established. Most sellers of nucs will not sell until the small colony is fully established with all combs drawn and the queen laying well, often well enough that the nuc is on the verge of swarming. There are some who will drop in the three pollen/brood/honey plus a few shook bees and a queen and send it out the door as is.
Here most reputable nuc sellers will allow you to inspect the nuc if there is time and you are willing to work around their schedule. Some may be just to busy especially during the height of the season but most will try to accomodate their customers even if it's not much more than a quick guided tour of the operation to let you know they have a good operation.
As far as how to transport. Most that offer local pickup will schedule a time right at dusk for you to pick up and when you arrive the nuc box will be closed up with a screen for ventilation. The general recommendation is to take them directly home and set them next to the hive you will be transferring them into and then the next morning do the transfer into the ten framer. Most local pick up sellers use woodenware and there will usually be a deposit you have to pay for the return of the woodenware unless you made arrangements for the purchase of the woodenware. Others use the waxed cardboard or coroplast nuc boxes and save on the cost of woodenware and deposits.
Around here a five frame nuc will usually go for somewhere around a C-note give or take.