Thanks, they worked out well. I went to the one in Auburn Hills because I happened to be there for work. They said they fill tanks in Ferndale, you have to drop it off and pick it up later. Even though I had a new 5lb tank from Midwest, I decided it was easier to just exchange it rather than fill it. It was under $17 dollars to exchange.
Note to co2 tank buyers from midwest: I should've saved $5 at midwest and just bought a used tank, rather than get a new one.
I also found they (airgas) sell a decent sized oxygen tank for around $115 filled - I need to ask how much future exchanges will be, but that didn't sound bad, considering the little tiny oxygen tanks at lowes or home depot are like $10. Anyone know if the williams regulator/stick kit work with these type of tanks too?