Yes, you need the bigdisk builder. It's at this site (I had to dig it out of my memory because I too usually depended on riocar.org for this)

http://rtr.ca/bigdisk/

From that page you want:
- builder_bigdisk_v3.upgrade (the builder)
- car2_v2b13_hijack.upgrade (the player)

With Emplode 2.0 installed, use it to install the builder, let it format the disk, then use it to install the player.

Then Emplode 2.0 should be good to get you loading songs on there via Ethernet.

Good luck! I am not sure I'd attempt it without the guide, and I *wrote* the damn guide. Let us know how you do!