Hi everyone, THANKYOU for all of your input!
For future options:
Where would I go to buy a large tank?( I don't know what sizes are avaliable)
How big is a 100lb. tank in comparison to gallons?
What do I do with the 500gal. tank here now, will Am. Gas come get it (and charge me for that to)? Maybe I should stop service and charge them storage fees.
Sorry for the delay in my responce, and thanks again,
Peter