I buy a lot of things on eBay and sell a few. I've had very few problems through the years. I always pay with a credit card through Paypal if that is an option. Three times (in about five years) the seller has failed to come through with the item I bought and I disputed the charge and got a refund. I've been told that the credit card is not obligated to credit the money to you when using Paypal, but I've never had a problem.
I would check the feedback of the seller and buy from someone with a good track record. I have some leftover vouchers from our Christmas trip to list and I'm hoping that the prices may actually go up a bit now that they are getting harder to find.
Sheila