Have you tried googling the company name to see if you can find out anything about them? It's great that they are agreeing to YOUR conditions and also that they will credit you as being the photographer of the photo. I'd suggest PayPal as the form of payment too and ... as I think FrillyLily said, just don't ever give out any personal information. If they say they need a bank account number or anything other than your name, for transferring the funds to you ... that truly is a RED Flag.
I too have had photos snatched off the internet. A few months ago I was googling and came across a photo of mine. I clicked on the contact-us button and sent a note asking them to remove my photo from their page and not to use any of my photos without explicit permission from me but I never got a response and my picture is still showing at their site. They took the photo from the Dave's Garden website and cropped out my watermark before posting it to their site. It's not a huge deal to me really because I'm just a novice at picture taking but there are some really wonderful photographers out there and if they can steal a novice's photo, I'm sure they can steal a professional's too.
