Hey Mark, I've been quietly following your Frankenferrari and other projects for years and I finally feel like I have something to contribute. I've been doing the consumer-level 3D printing thing for about 5 years now. I took the long hard road and built my own printers from scratch since kits were not really available until fairly recently.
I'm not specifically familiar with the FT-5, but I can tell you that in the world of 3D printer kits, you get what you pay for. Lower price point kits have cheaper parts but the good thing is, you can always print out a new part! As long as the frame is solid, you can customize everything else. You and your son will have fun with this. Lots of cool stuff to make. Have a look at
http://thingiverse.com to see the thousands of things contributed by the open source community.
On the topic of sanding/polishing the parts, if you're using ABS, there's a trick known as an "acetone vapor bath" to smooth out the layers:
http://sinkhacks.com/building-acetone-v ... ted-parts/