I havent seen too many banshees without the chain whack, that's pretty normal. It usually doesnt affect anything, and you can even take a die gridner and clean it up.
As for the VIN, he sounds like he knows what he's talking about. In NJ anyway, if you buy just a frame brand new, or make a frame from scratch, it won't have a VIN, the state will issue you a VIN, and it's up to you to put it on the frame somehow. Not everyone does that, but you could get into trouble for it.
If you have a title or registration and there isnt a VIN on the frame, you have to do 2 things:
1- Have DMV run the VIN you have, and make sure it isn't stolen, etc.
2- Get that VIN number on the frame, and then register it/title it in your name.
You might want to check with your state's law just to be certain, but thats how it works here in NJ.