You would have to have some kind of super-over-zealous prosecutor to try to charge you with anything for just looking over a friend's inherited guns to assess what they have. If you see anything illegal or suspicious, advise them of it and that they should contact the authorities for instructions, and walk away. Or worst case, advise them that you are obligated to call the authorities about anything illegal, and tell them it would be a really good idea if they were the first ones to call and not you.
If it turns out something is illegal, and the cops ask you about your role, just tell them you were a friend who "knew guns" and they were curious as to what they had, and you told them. End of story.
Most likely, it's a standard semi-AK-clone or even an SKS or some other eastern-block rifle. Hell, it might be a Mauser.