Hey, this isn't too difficult. Although, I would use Formlists instead of leveled items, and I would make the card pack a book, instead of a misc item, that way you can use the event OnRead(). Here's a script that should work:
Scriptname LagruejCardPackScript extends ObjectReference
Actor Property pPlayerRef Auto
Formlist Property LagruejCommonCards Auto
FormList Property LagruejUnCommonCards Auto
Formlist Property LagruejRareCards Auto
Event OnRead()
Int A = Utility.RandomInt(0, (LagruejCommonCards.GetSize() - 1))
Int B = Utility.RandomInt(0, (LagruejCommonCards.GetSize() - 1))
Int C = Utility.RandomInt(0, (LagruejCommonCards.GetSize() - 1))
Int D = Utility.RandomInt(0, (LagruejCommonCards.GetSize() - 1))
Int E = Utility.RandomInt(0, (LagruejUnCommonCards.GetSize() - 1))
Int F = Utility.RandomInt(0, (LagruejUnCommonCards.GetSize() - 1))
Int G = Utility.RandomInt(0, (LagruejRareCards.GetSize() - 1))
pPlayerRef.AddItem((LagruejCommonCards.GetAt(A) as MiscObject), 1)
pPlayerRef.AddItem((LagruejCommonCards.GetAt(B) as MiscObject), 1)
pPlayerRef.AddItem((LagruejCommonCards.GetAt(C) as MiscObject), 1)
pPlayerRef.AddItem((LagruejCommonCards.GetAt(D) as MiscObject), 1)
pPlayerRef.AddItem((LagruejUnCommonCards.GetAt(E) as MiscObject), 1)
pPlayerRef.AddItem((LagruejUnCommonCards.GetAt(F) as MiscObject), 1)
pPlayerRef.AddItem((LagruejRareCards.GetAt(G) as MiscObject), 1)
EndEvent
Attach this script to your card pack book, and it will run whenever you read the book. Make the formlists and add your cards to them, I assumed they would be misc items. Don't forget to fill properties in the creation kit after attaching the script.