Possible stupid ?s, I've never used propane before.

So I've got this nice new aluminum propane tank, what I see is you
exchange the
tanks, something I don't want to do, I want my tank back, is this
normal request or am I
going to get a blank stare?
I assume if I have to leave it they will give me a receipt and if I
get the "you don't receipt",
I should just walk out?
Is Suburban or Eastern propane ok?
Does the tank have to be completely empty?

thx, Tom