So I ended up doing this properly by re-soldering the transistor. I'm happy to report it worked and now my nav turns on all the time, but it wasn't easy. It took me about 5 hours and I have a lot of prior soldering experience and equipment. I don't recommend this method for novices, try the screw method instead in the link.

While I don't have pictures, here are detailed instructions for soldering:

1. Take the DVD drive out following the guide above. Unscrew the board from the back that contains the DC-DC converter in a metal box.

2. Remove the metal box by desoldering the 5 pin connector and the connectors on the edges of the box. Desoldering the edge connectors is especially hard since the heat dissipates into the box so its hard to get the solder hot enough to remove it. I used a hot air gun to get the solder to melt and then a desoldering pump to remove the solder. What complicated it further is that you need to untwist the metal traces going through the board to be able to take the box out (as they were twisted AND soldered during installation), and then remove the rest of the solder and then you can take the box out.

3. Pry open the box to take out the DC-DC converter board out. The box is soldered together in places, but just prying gently with a flat screwdriver worked to get it off. The board is taped to the box in some places, gently try off the tape and take the board out.

4. Remove the white glue over the coils and where the transistor is. I used a soldering iron to melt through it and remove it piece by piece, but it may be better to heat the whole thing and try to remove it with a tweezer. In any case this is a mess and takes a long time. Be careful not to remove the transistor as you my lose it, and don't melt through the blue coils labeled "100" as you might damage them. Get enough glue off so that you can take out the blue coils.

5. Desolder the two blue coils labeled "100" that to allow access to the transistor. I'm not sure if their orientation matters (it likely does not), but to be safe remember the way they were oriented and but them back the same way.

6. For me the transistor came off with the second coil, but if it doesn't, desolder / remove the transistor, use a fine tweezer as it is tiny. Most likely if you are having problems the transistor will come off right away. Once its off, try to remove excess glue and gently sand the connectors and sand the traces on the board. I used a 1000 grit sandpaper. There is only one way the transistor can orient on the board, so don't worry about that; worry about losing the transistor, its so tiny that if you flick it somewhere by accident you probably wont find it. I suggest you do the whole thing over a white newspaper so when it flicks off you can find it easily.

7. Solder the transistor onto the board. Its difficult. The way I did this is I first soldered the top contact by dabbing some solder on it while aligning it properly with a tweezer. Then the transistor stayed in place while I soldered the source and drain contacts properly, and then I came back to the top contact and resoldered that connection. I used a loupe to be able to see the connections at the end to make sure they are solid.

8. Solder back the blue coils and solder the DC-DC converter back to the board via the 5 pin connector. I did not bother to put the metal box back on since it was bent from prying and I'm not sure what purpose it serves. Before you screw the player back on, connect it to the car to make sure it works. If it does not work, I suggest checking your connections and, if you have the equipment, hook it up to a 12V power supply to try to get the 5V on the output pin so you can debug faster.

Again, this is a lot of work and has a good chance of failure. For me I figured my nav does not work anyway, so I have nothing to lose (I can always just leave the nav DVD disconnected). And as a disclaimer, I take no responsibility if anything happens to you or your car . Good luck!