I've never ordered warranty parts based solely on the word of a homeowner. If the person doing the inspection is a licensed HVAC contractor, they can generally get warranty parts by dealing with the local or regional Carrier parts outlet. If they're not licensed, then they won't be able to obtain warranty parts.
Also, our company policy would not allow the homeowner to install a heat exchanger we provided. Installing a HE isn't too terribly difficult, but if it's done wrong the consequences can be deadly. Also, warranty repairs performed by unlicensed persons could void her remaining warranty.