modsquare

I have a question about about the Millennium Falcon lego set number 10179. I found a collection of 22 Lego sets at an estate sale. Most of them were unopened and still in their original boxes. I bought the lot for my 10 year old son. He assembled most of the smaller sets and was just about the assemble the Millennium Falcon when a friend of mine pointed out the value of the piece. Unfortunately he had already opened the box but hadn't yet opened all of the individual bags. I was wondering since he has already opened the box would it devalue the piece any more if I was to let him put it together? He has opened half of the bags already.