Return a a computer they custom built

Hello! I checked the forums and couldn't find this specific question — I just picked up a custom built computer from Microcenter yesterday and it unfortunately did not help with what I needed it for. I know one can return parts individually purchased, but I didn't know the process for the entire build. I have all the boxes, is it implied I should disassemble everything and re-box it? I'd be worried about doing this which is why I had it built and got the extended warranty, or is it advisable to just bring the whole thing in with all the boxes/packaging separate?

Thanks!