You can try appealing the decision, but I don't think you have much chance of succeeding. EBay will only be concerned with the kit itself, not with any information provided.
As a business seller you're required to accept returns anyway, so the only difference between a customer return and a money back guarantee claim is whether the buyer pays the return postage. Theoretically you may have some rights if the kit is returned devalued in any way, but don't count on eBay taking much notice even if it is.
EBay's treatment of returns and complaints is very much biased in favour of the buyer. EBay itself has told some sellers (but not publicly) that fraudulent returns and items returned damaged or are part of selling online, and they advise sellers to allow for this in their pricing.
