I have had a couple of requests for this information and have finally gotten around to putting something together. I hope it will be of some help.
The original built in temp controller burned out on my machine. FF does not sell replacement parts and postage back and forth to the official repair shop was going to cost about $75. And then there would be the repair cost. Being a little cheap and handy I decided to try doing the PID install on my own. I started by reviewing a Silvia mod done by Skene Design. His site is: http://www.skenedesign.com/Silvia
The FF does not have as many features as the Silvia but the fundamentals are the same. I used material from Aubers, their site is http://www.auberins.com
Material: 1. Aubers 1/32 PID
2. Aubers 25amp SSR
3. Aubers Miniature RTD
4. Motorola 5v cell phone charger, any DC supply between 3-32 v will work I just had this around
5. Male and Female spade connectors
6. Hookup wire
7. 2 ln4001 diodes
The set up includes steaming by using the alarm connection on the PID and the DC supply.

I do not have a diagram of the original electrical layout. Sorry, so all you are going to get is the final layout.
I chose to install the PID in the face of the machine. I cut the hole with a jigsaw and adjusted the fit with a file. Be careful to leave space for the boiler supply tube. I should have moved the PID over to the side another 3/8" to leave more working space. As it is I had a hard time getting the wiring in place without disturbing the supply tube.

The cover would go back in place but I never got it there. The clock would fall out as well so it and its internal cover were removed. If you do decide to leave the cover in place insulate the boiler to help protect the PID from over heating. The PID could also be mounted in a project box screwed to the side of the machine.
The SSR is screwed to the back. A little heat transfer paste couples the SSR to the metal back. Space is limited so the wiring had to be completed before installing the SSR.
The DC supply was small enough to slip in the other rear corner.
The wiring removes the original ready lights. The PID is used for the brewing and steaming temps.

The diodes are covered by shrink tubing. Where possible I saved the existing wire and spade connectors. I never got around to shortening all of the wires to make the install look well finished.
The buttons work the same as the originals.
The upper button starts the pump. The lower button activates the alarm function on the PID which puts the boiler in steam mode.
The RTD is installed in the same well as the original. I only changed the heat transfer paste.
The programing for the PID I set at:
P- 3.7
I- 858
D- 165
Set point 205
AH1 255
Al1 256
I tried using the auto tune function on the PID but found the settings made the boiler respond to slowly.
I found that 255 degrees was plenty to keep the boiler on while steaming. It was also plenty below the trip point of the thermal fuse.
If the boiler heating element goes the GFI will still trip the same as in the original.
The machine was in service for two and a half years with no problems. The only adjustments I made were to the PID program.
Now it sits by it self collecting dust having been replaced by a Bric.

I have an X5 with the same problem, and was thinking of reviving it to compliment my lever, and just to fool around with PID, preinfusion, and so forth for kicks. I was looking at the Auber website and I wondered if I could adapt one of their Silvia kits or if I should just purchase everything separately. I presume the only difference between their preinfusion kit and the lower end ones is programming on the controller? How hard are these things to program?

Also, why did you need the DC supply here?

Cheers,
Colin