I have yet to install "Hijack" as I only just got my PC working again (I far prefer my reliable Mac). I realize that initially I will need to do this by serial cable.

After doing this if I want to use JEmplode to update the player over ethernet, update the hijack kernel periodically or just use Emplode from my PC over my home network through my router, will the fact that my ISP is PPPoE based and offers dynamic IP addresses (which change regualarly) affect me?

I am not very knowledgeable about computers but I understand that the dynamic addresses can cause problems if you are expecting to use a fixed IP address. Or is the address assigned through DCHP (which doesn't change) the one I use? i.e. 192.168.1.1 etc

The first thing you need to do is make sure you're behind a hardware firewall/router. You did not say, in your description, if this was already the case.

If you use PPPoE, then the router handles the dynamic addressing and everything INSIDE your network is fine and is all 192.168.x.x addresses and there's nothing to worry about.

More information, and a diagram, can be found here.

Sorry yes I'm using an ASUS router which is setup to access the internet through my ADSL modem via PPPoE. I currently have a PC and Mac linked to the router. So if I connect the player to the router by a CAT5 cable and search for it through JEmplode or Emplode it should just find it automatically? I suppose really I should just connect it up and see and come back if I encounter a problem.