I've sold plenty of used items on EBay and I have a no returns policy. However the items are honestly and thoroughly described, always start with a low price, plenty of pictures (the max 12 which is allowed), and I ship to the USA only. Never had a problem. Am not sure of the "parts swapping " situation though. With old electronic items I always state that due to the age of the item there are no refunds because honestly, it can be working fine one day and kaput the next, especially with electronic items. I'm at 700+ bought/sold with 100% feedback.
I've also seen those who sell with a no returns policy and that has not deterred me from bidding. I do look at their feedback score though and anyone with a score less than body temperature gets a thumbs down hihi.