In my opinion, and after owning the original note as wekl as the S3, I would have to say that that os a deal that may be favoring your friend.
I also like the s pen and now have a note 2.
The reasoning behind my conclusion is the sole fact of the hardware. The S3 has the quad core processor and 2 gb of ram just to name two items.
But don't get me wrong, the original note can still be a usable everyday device for most people, but I see a fair trade as possibly a S3 for a note 2 straight across.
The note 2 was standard with jelly bean like the S3, and the hardware specs compare favorably between the two. Price wise, they were about the same when new as well.
I mean a S3 for a note, plus maybe a nice case or accessory would be a better deal for you. More even in my opinion.
It's not wrong to fondle the s pen.