I don't have any experience re-installing the old radio, so I can't comment on that. They'll probably have to do the standard VIN unlock.
That's a bummer about the VSS not being connected... I guess if you want something done right, you have to do it yourself or hold a shotgun on the techs while they do the work!
VSS = Vehicle Speed Sensor. The NAV systems use this signal to help map the vehicle's progress when it is getting little or no GPS signal. It is also used to "lock out" most of the NAV functions when the vehicle is moving.
The VSS circuit was not added to the 2003 H2s stereo wiring because NAV was not available at the time. To retrofit the VSS, a wire needs to be added from the speedometer circuit to the stereo connector.