tavager, do you have vBCredits? If so, create a new currency and merge it with the one used by vBPlaza. Then when you get rid of vBPlaza you just need to set the vBShop to use that new currency and it should already be populated. You can test this by disabling vBPlaza instead of deleting it. If it doesn't work, enable it and we'll see what the next step is.
And by the way, I do *NOT* work with or for DragonByte so anything they tell you trumps anything I say. I'm just a busybody who has almost all of the DB products.