I've never done it - but to exchange a tank, I don't think it would be an issue.
And flabob - Petco's have the sale 4 or 5 times a year (seems like more recently) You just have to check in from time to time. You can ask the employee's working there and they'll usually tell you. There are sometimes threads that pop up announcing the sales but they happen so often anymore that I rarely see the threads. When the sale was once or twice a year it was more of a big deal.
They actually wouldn't Exchange it or give my money back because its passed 30 days. Lesson learned!
I can tell you it wasn't going on yesterday... Lol. I think you have to swing by every now and then.
How do you find out when petco has the dollar a gallon sale?