You don't need a GPS receiver, you need a GPS antenna (there is a difference, and they are not interchangeable),
Your documentation is your order, which should read Ford SD satnav with touchscreen, or you can check with your VIN on ETIS. The user manual covers several models ( if I remember correctly).
You can either replace the GPS antenna on the roof (the knobbly base of the radio antenna), or get a patch antenna, and install it somewhere on the IP (you need to take the satnav out to connect it, but this is the cheaper option).
You can get the SD (which has to be the correct Tomtom SD for your Ford system - there are several) online (e.g., http://www.navishop2...products_id/919 ), but Ford could actually be cheaper, esp. if they have a sale on maps like they did last year.
There is no switched live feed (IGN) on the original quadlock, as the OEM radios are always powered ( and get their switch signal from the CAN bus), you need a CAN adaptor to do the trick (or always switch manually).
This sounds like a known issue with the Bluetooth module (which is not the radio), which may hang up and not communicate with the radio anymore, at which point the radio acts as if there was no Bluetooth module installed. This should recover after a reset (fuse or battery disconnect). Don't forget to have the radio PIN code at hand before you try this.
There was a free replacement action for satnavs of about that time. Have your dealer check TSI 26/2013, if that is still active and applies (btw., result of a google search on travelpilot fx tsi, but I recalled there was something to search for).
- Voice commands to be played through the car speakers & music to be muted during the command
That's the tricky bit - as there is no standart/implemented way for the satnav to tell the radio to mute and play it's output. There are hardware solutions to connected between radio and speakers (e.g., http://www.ge-tectro...e-FastMute.html). Other options are to also play music via the Bluetooth device (mobile phone or PND/satnav), so the muting / audio priorisation is done in your device, or to wait for the European launch of Applink, assuming that it will be made available for "older" cars with Sync, and there soon will be navigation apps supporting Applkink for the large major platforms (IOS and Android).
1) No (even not knowing what you might think "the ECU" ist - that is a generic term for any Electronic Control Unit in the vehicle, and there must be more than 20 in yours). Can you set the clock on the cluster with the OEM radio gone? If not, you may need to disconnect the battery once to let the modules (ECUs) relearn the vehicle configuration without the original radio.
2) No idea - what ever does one get directly at the Ford dealer?