Adblue Bluetec Service Lights and Warnings

2009 M320 Bluetec : my dealer seems to have problems adding fluid and resetting lights. I had to go back each time I had the car serviced so far. There is an Adblue Low warning and ...... there apparently is a OBD2 "Check Engine" light warning, that my handheld reader does not produce a code for (its blank) and it will not reset the light. Last time the Dealer fixed the CEL by reprogramming the computer. Odd corrective action.

I have NO IDEA how I would reset the screen "Low Adblue" message if it popped up again....no idea how the "logic" works to make that message come on.

My question: If I add a gallon or so after about every 1000 miles, will the "logic" detect that the tank was serviced, or is this a "dumb" mileage counter- triggered light? Is there a OBD2 code associated with Adblue ?

Another stupid question: there seems to be a lot of concern about "contaminating" the Adblue fluid itself. Just how paranoid do I need to be when I handle that stuff....and understanding there is a 2 year shelf life limit....can I store unused portions of that stuff in the original container for a reasonable period of time?

Any helpful insight would be appreciated. Thx