I was told as a rule of thumb figure 1000# for a 1000 gallon tank.  Some older ones weigh more.  The 300 gallons of LP will weight about 1300 pounds.

DO NOT lift it by the eyes. They are generally rated for 5%.  Run chains or straps all the way around it.

Legally it should be pumped down to 5% or less.  It should also be placarded, have shipping pappers, driver to have CDL with tanker and haz mat endorsements.