Yeah, going down that item list, most of those items look decent. Even the "no-name" stuff (that you may not have heard of) like Kalloy are good stems/seat posts. They might not be the fanciest/lightest setup but you'll definitely get many years out of them. Usually complete bikes have a lot small items they try to cheap out on....like headsets, bottom brackets, etc.. but that bike actually has good stuff for that price range.

Only thing you may want to immediately upgrade is the seat but that's mainly a personal choice...it may feel comfortable to you, it may not. What feels comfortable to one person can feel like a rock to another.

I would definitely go with the complete. Since you haven't spent a lot of time riding, it will give you a good base to figure out what works for you. Friends of mine have gone into bike buying with the same intentions and ended up keeping 95%+ of the stock components.