Yes. The mod can be done. I've done it twice. I bought the same stereo as the one on my '05 Altima... from Ebay to try it out first. The mod took about an hour. Once I successfully tested the unit... I pulled the head unit from my car and performed the same mod. SUCCESS!
The difference with my mod is that I didn't go as far as adding an RJ45 connector... and I have a cable leading out of the head unit, down towards the shifter, and mounted DPDT 3.2mm stereo jack next to my 12V power receptacle opposite the hazard switch. One prerequisite needed for this setup to work, is to keep an audio CD in the machine. Once the cable from mp3 player is plugged into the jack... the CD audio signal will be cut off and the mp3 signal pass through.
One thing I realized I should have done after all was completed... was to add a ground loop isolating ckt within the head unit to eliminate the whine from the alternator. Granted, there is no whine when playing from mp3 player's headphone jack to the input. But if you use the docking connector (with power) like I do... you may hear a slight whine as you press the gas pedal. This also happens to my JVC hu with AUX built in... so I guess it's normal. I just use an external noise filter in-line from player to jack.
As for the test head unit... I'll probably put in back on Ebay.