Ok, so now that we have established that Mel does not take criticism well, Jason is here only to instigate trouble, and Adam likes drama and runs his mouth off. But its ok because we are all fucked up in some way or another and all here because we love the hobby. But none of that really helps the OP.
My advice is to look lots of places for information before you buy. There are a lot of sites, and all display different information in a wide range of formats. None of them have all the information you need or guarantee to be 100% correct all of the time. Not all of them endorse only sellers that i would put on my own personal trusted list. Not all sellers always know or disclose exactly what it is they have for sale, even the best out there. The good ones, however, will make things right if there is an issue. Sometimes you can get a good authentic poster at a good price from a known whack job. What you gain in price, you sacrifice in security when dealing with these types. If there is a problem, they will put their own arm into a wood chipper before you see any money back. But, this shouldn't steer you away from someone just because their wares seem to be cheaper then everyone else's. Sometimes lower prices are just that, and you see no appreciable drop in service or condition!
In the end, there really is no substitute for experience. I'm willing to bet that every one of the more experienced collectors here has been burned once (or more) when purchasing. The nature of the hobby combined with buying things online with just a photo as representation of the product make it inevitable. We all can try to give you experience by proxy, which is helpful, but not the same thing. Take it slow and do a lot of research before opening the wallet. You will be glad you did.
Oh, and very nice stuff Conor! I have several of those on my list.