Has anyone had the full dash system installed? Price? Am I gaining that much more info than I already have with the factory installed system?
The Silverleaf, whether standalone or the VMSpc version, is an excellent display system but the fact that you ask that question makes me think the money would not be well-spent. Some drivers feel the need for more tech info about their vehicle operation, though I'm not sure they all actually use that info very much. The factory-supplied dash provides all the info a typical RV driver might want or need, so buying a pricey electronic dashboard makes sense only if you are really interested in more detailed info, have some understanding of what that info means, and are willing to monitor it.
You seem to be asking if the system will provide extra value, but that really depends on YOU. If there is info you want that is not provided by the standard gauges and indicators, then you should consider one of the enhanced dash display systems. Since you don't seem to have an unfulfilled needs, I would say there is little or no value in having it.
A less techy alternative is the TripTek system from Coretronics. It's more of a trip computer than an engine monitor, but it includes display capability for several items not usually provided in the standard dashboard. Some TripTek models also include monitoring for the SmartTire TPMS. Less technically oriented drivers may find it more in tune with their level of interest.
Yes, the Silverleaf can display the status of Pressure Pro tire sensors, though it requires the Pressure Pro Gateway add-on to do it. You don't gain any functionality as far as tire pressure monitoring is concerned - you just include the TPMS info on the Silverleaf display. That's convenient if you utilize the Silverleaf as you primary visual dashboard.
If you your concern is the capability to display additional chassis technical info when & if something goes wrong, you may want to learn more about the capability of the dash on your Phaeton. The standard Freightliner chassis dash includes a small window (the one that normally shows the odometer) that is capable of showing a host of additional items via a menu of choices. It's not a really convenient user interface and impractical to use while driving, but it does give access to quite a bit of data. I believe the '07 Phaeton has the Freightliner MMDC panel display unit, which should be described in the chassis owner manual. If you don't have that, see theses sources:
http://www.rvtechlibrary.com/electronics/mmdc_overview.php
http://www.rvtechlibrary.com/electronics/mmdc_owners.pdf