Replacing head unit in Gen 1 Prius

So this is a nebulous topic apparently. With a lot of digging I have found that apparently a specific model of jensen head unit came with a microcontroller that allowed it to talk to the prius controls ( angelfire (the domain name) / electronic2 / mp3hack ). << Can't post links.

Honestly I care less about it talking to the prius controls than it simply connecting up with the built in woofers. The audio button on my Gen1 doesn't work and so I have no way to adjust balance or EQ (thankfully the EQ is flat and the balance centered).

The MFD is a step above worthless, so I'm considering a project to replace the MFD with a small tablet connected via bluetooth to a OBD-II reader. This way you have access to all the same information and the tablet can be connected via aux to the headunit.

Before going to any of this trouble I would like to know if there are any significantly easier ways to upgrade the head unit in the gen1?

It should be noted that my existing head unit is functioning.