OK, as one who has done this multiple times, the last was in April after Harry Potter opened.
1. Get the earliest time as possible.
The basic procedure is head to the Valet parking (easiest access is to take the I-5 to the 101 north to the Lankershim Blvd exit, make the right, and then another right at the large sign and go up the hill to the Frankenstein Parking Structure and Valet Parking Entrance. (That is one off-ramp past the main Universal Studios one).
2. Walk to the entrance, and then go through security, to the right of the main turnstiles will be a VIP Check In door, no matter what time your actual reservation is. If they need you to return, they will get you into the park through another door and let you know when to return.
3. You are brought to the meeting room upstairs, where there is a light breakfast buffet area and when you get to find your host and other members of the group. (Usually under 20, usually size is 12 to 16).
Then the park makes a decision as what to do first, two main options. (Decision is to help keep waits low for everyone)
Place you directly on the enhanced Backlot tour, with a private vehicle that only has your group, though sometimes two. This tram does have multiple stops where you get out of the tram to walk through a soundstage, the Prop Warehouse and more. (All subject to current filming and does change frequently). It last about 3 hours on average.
Or a walking tour of Wizardly World of Harry Potter, and the Front of the Line access to the rides (though there is no requirement to do them), and special access to the Magic Wand Shop.
And then in the morning, you get the other of the two options mentioned. Later check-ins might get lunch in-between the two.
Then you are taken to the special private Lunch Buffet, which is very upscale and near Minion Madness on the upper level.
Then you have a more relaxed experience that is more flexible, and if you opt, can just go on your own.
But the host will tell you specific times to meet up with them at specific shows for special backstage access. The park knows that not everyone wants to do every ride for multiple reasons. So you can opt to use the host more or be more free. (Remember that the Host has to get their won breaks for meals, breaks, etc. and is designed to allow that to happen).
Your VIP Pass will allow you Front of the Line (also known as Gate "A") for every attraction, and reserved seating for the shows (if there at least 10 minutes prior to start). And unlike the cheaper Front of the Line passes, unlimited trips on attractions, in fact, you could go back to Wizardly World and ride those attractions again.
I highly recommend it if works in your budget.
And yes, you can get an re-entry stamp and come back to the park. Your VIP Credential has a bar code that is only valid for the day issued, and is good from open to close.
Hope that helps.