Your DEF tank is plastic - no matter what color it looks. DEF is clear but if you let it dry out, you will get a ton of white crystals (which are urea). Check your documentation but DEF tank volumes are 6 to 12 gallons. You can use the weight of water (8 lbs/gal) if you are concerned about weight. I would not worry about weight - you don't worry about the weight of 13 qts of oil in the engine do you? A full tank with the V^ diesel is good for 6-8000 miles so keep a jug and top it off before a long trip.
Since you are unfamiliar with diesels, here goes:
1. Diesels ignite the fuel air mixture with compression. They do use fuel injection to inject fuel at the precise time to ignite it. Fuel filters need to be kept clean and fuel quality is very important.
2. Like all internal combustion engines, diesels have pollution control systems. Similar to cars but very specific to diesels. First up is the DPF or diesel particulate filter. This catches the soot produced by combustion (diesel fuel is not as highly refined as gasoline) which is a major component of air pollution generated by diesels. The DPF is monitored by the engine computer and when it is dirty enough, it is regenerated by burning a big load of diesel fuel in it.
3. The second major pollutant of diesel engines is NOx or nitrogen oxides. Two systems are used to control this - the EGR exhaust gas recirculation valve, and SCR or selective catalytic converter. The SCR is the component that uses DEF (diesel exhaust fluid) to react the exhaust with a special catalyst that converts NOx to nitrogen and water.
Diesels don't require much maintenance - clean fuel, clean air filters, oil changes once every 15,000 miles or so, DEF, other than those few things, enjoy driving it. One other thing - do not idle it for long periods of time. It won't warm up and you will plug up your DPF.
