It may seem obvious to old hands, but here's a tip for you: eventually everyone seems to come across a seller who is untruthful, unprofessional, unhelpful, rude, or even threatening. I know I have.
If you don't want to risk this happening to you, then BEFORE YOU BUY simply click on the eBay rating shown next to the seller's name and you will get to the feedback chart. Clicking on the Negative icon for say the 3 month period, allows you to see NOT ONLY what has been said about them when things have gone wrong, BUT ALSO what the seller has said in reply. These can be anything from apologetic, which is fine, to abusive, vicious and insulting (which we can all do without).
Avoid sellers who appear to treat their customers with a lack of respect!