How can I do a purchase safely on Ebay (details inside)?

Sorry if this sounds like a stupid question but this is the first time I’ve bought something online, so I’m a bit worried.

A long time ago I had been looking for a rare item. One day I found it being sold on Ebay by a shop. That shop had its own website and can be displayed on Google Map (it seems that the shop uses the website to sell locally and Ebay internationally). I looked at the shop’s Ebay profile and saw that it has been on Ebay for a very long time and is rated positively by many. So I’m fairly sure the thing being displayed on the page is legit.

The thing is, I can’t buy directly, as there are too many things involved that I can’t do: currency changing, customs procedures, Paypal… so I need someone to do all those things for me. I had to go to the Vietnamese site of Ebay where they offers to buy my item and send it to me. So far that is the only solution I can think of if I want to buy anything.

Now the question is: can I trust that service? I can’t find any review on that service anywhere on the net. There are some bad reviews on the Vietnamese eBay scattering around but they are all from people who directly buy items displayed on ebay.vn, not from another site and through the service. The ebay.vn site is full of good reviews, but they can be bogus. How can I purchase my item through the service safely?