I guess i will be the first to say that you shouls have a professional assemble the bike. Out of the box there are many things that still need to be done for the bike to be properly assembled. One of the hardest would be spoke tension, I have rarely seen a boxed bike that does not need this adjusted. For this you will need a spoke wrench and the knowledge of how to do it. Do you know how to adjust the derailleurs on a bike? Have cone wrenches and know how to use them?

I could go on and on. If you are really set on purchasing a bike online from Costco you should pay to get it assembled at a LBS, one that has trained staff. Yes you can learn how to make everything work properly, but you will spend more on tools and spend a whole lot of time as well.

just my 2 cents.