White smoke could mean many things - but on a cold morning, its unburned fuel going out the tail pipe. Is his glow plug light cycling? Is it starting easy or hard? Hows the oil consumption?
With all the white smoke, I'd guess he has a rough time getting it started. The glow plug electrical harness is notorious for breaking wires. Theres a lot of current running through those little wires. If the glow plug light isnt cycling, the culprit is probably the glow plug controller on the right (drivers side) head in the back - little can with all the wires on it. If all the glow plugs are working correctly, or at least the majority, and it starts easy, rest assured that the compression is also acceptable, I'd probably start looking at the injectors.
A local diesel place cleaned and tested the injectors in my 6.2 for $15/ea. I think their fairly inexpensive to replace also - around $45/ea. 190K miles is getting close to the limit on a 6.2, mine only made it to 140K before needing a rebuild.
