If you ask just about any female above the age of 13 what kind of wedding ring she likes, she will most likely give you some spill about metal colors or size or cut or shape. It is something we think about, it's in our blood! And when you dream about that ring for years (and years) it could be extremely devastating to get something that is completely different that you hate. I know that all the guys reading this are probably thinking how ungrateful that sounds and that it is not about the engagement ring, it is about the meaning behind it and what it symbolizes. True. But regardless of how stupid you think it may be, you want her to love her ring as much as she loves you. She is after all going to wear it everyday for the rest of her life, right?! So, with that in mind....guys, try not the be offended and sensitive about changing the ring, you want her to be happy.
If you are a female finding yourself in this situation, my best advise to you is to simply be honest with your man. Tell him you love him and you want to be his wife, but that you have a certain kind of wedding ring in mind and ask if he would mind an exchange. If you fear he might be angry or upset then make a comment about someone you know exchanging their engagement ring to see what he says and how he reacts. Upset or not, it comes down to you wearing a ring you hate, learning to love it anyways, or sticking your neck out there in an effort to be happy with what you get. I suppose it is all a matter of what you can live with.
I'm sure that someone, somewhere will have stories about how such an exchange might be bad luck or wrong, but that is going to be a matter of opinion. So, I would say if the two of you feel ok with the exchange then go for it. If you are truly concerned, then ask someone you look up to (a parental figure) or your minister. They will be able to tell you how your family or your religion might feel about it.
As for the actual exchange at the store, it will depend on the store's refund and exchange policies. They will definitely want all the original paperwork, receipt, etc and could possibly have a very short period of time allowed for exchanges after the initial purchase. If your wedding ring has been engraved, customized in some way or if it was a closeout or discontinued design then you may be out of luck. Your best bet is to simply take the engagement ring back to the same store where it was purchased along with all the paperwork and ask them what your options are as soon as possible.
If a return is impossible for some reason, there are still options. You could consider having the ring reset or restyled into something you do like or try selling it and use the money to buy another one. All that really matters in the end is that you and he are happy together and that both of you can live with your decision.....and the wedding ring!