What if I should ever need to replace some of the other hardware like the StrongArm and the "mainboard"? And is there even a mainboard per se?

Yes, there is a mainboard. There is a video in the troubleshooting section of the FAQ that shows how to replace the mainboard.

As far as replacing individual components on the mainboard, well, whether or not to do it is up to you. It involves soldering very small surface-mount components. If that's something you can do, then it's possible to repair components on the main board.

If this stuff goes out, am I just out of luck ?

Click here to see my opinion on this topic.