He is best advised to show up with a full seabag and any items that he would need to spend time onboard, maybe even overnight. I am not familiar with the schedule of the TR, but I'm sure someone else here will be. He should already have an assigned sponsor onboard the TR to advise him on schedule as well.
He will be extremely limited in the storage space he is allotted, but most junior sailors are able to fit their seabag items plus personal stuff (books, CD players, laptops, etc) in their lockers if they are creative with their folding and rolling.
He can expect to hit the deck running, because there likely will not be a great deal of personal time once he is all checked in. Words of advice...qualify, qualify, qualify. Nothing will earn him more respect than becoming a useful body as quickly as possible.
Otherwise, it's just something that every new sailor/nuke has to do. It is extremely intimidating the first time...I'll never forget mine. M Div berthing is a trip.