If its sold through Amazon, it's a piece of cake. You return something, and they send you an e-gift cert for the amount of the return (and right away, too, from my experience). If it's sold through a 3rd party, different ball game. Have to look at their terms.
Amazon is AWESOME about returns. I bought a City Mini GT from them, used it, and discovered it wasn't "all terrain" enough to handle our gravel driveway. They let me return a *opened, used* $350 stroller no problem. You just follow the prompts online for a return. Or you can call them, and they'll email you a link to print out a return shipping label. Depending on the item, you can get a refund immediately or you may have to wait until they receive the return. The latter is what happened with the CMGT.
I sent back my City mini when I upgraded to the elite and returned several other things. Super easy, just drop off at a UPS store or they will pick up from you for a fee.