I have a GMC Denali, a Bikes Direct SST, and a build up from a Nashbar Aluminum Road frame. I bought a Bikes Direct Hays MTB for my son, and for my wife an Aggressor GT from Performance Bikes, our only bike store bike. (I have approximately 40,000 miles on those three bikes over about 7-8 years)

There is nothing wrong with upgrading the Kent road bike, and IME literally no benefit at all from using a local bike shop for an entry level bike. The Kent is going for $129 right now, and I expect that anything you replace will be an upgrade. Replacing those parts are cheap if you do it yourself. I suggest just upgrading anything that breaks or wears out.