You PROBABLY have nothing to worry about. Based on the picture alone, both the medal and document look "right". I'm not aware of either the medal or booklet being faked. There is not a lot of financial incentive to fake the medal or green ribbon and the booklet would be harder to print from scratch due to the red cover. Again, you are PROBABLY OK on the basis of the photograph. That being said, it is your money and I wouldn't pay an exorbitant sum - I personally wouldn't pay more than $30 for the set.
This is a more contemporary Russian Federation made award. Since the Democratic Republic Of Afghanistan no longer exists they are being "awarded" by some sort of "Umalatova" type affair. The latest documents are a simple unfolded glossy piece of paper which can be folded when awarded but it definitely not a "booklet".
There certainly may have been (and may still be) some "enterprising" Soviets (or Russians or others) producing these (not sure why though). Not coming out of Afghanistan though.