It doesn't change as far as I know. I've brewed it partial mash, with a partial boil with the same instructions. It was a damn fine beer to be sure. Just go with what is already written. The only difference I think you may see between a partial and full boil is possibly hop utilization and color of the finished product. There may be more to that, but I don't know. Like I say, it was a great brew with following his instructions even though I did a partial boil. The only variance I had from his recipe is that I dry hopped a 1/2oz of Amarillo hops that I had lying around.
EDIT: Sorry I didn't realize that you are doing a straight extract brew, I don't think my advice changes the facts. But one other fact is that the extra step up to doing a partial mash is NOT difficult and reduces the amount of (expensive) malt extract needed. Make the jump!