Look at the sellers feedback. Bad feedback? How long ago and for what? Every seller, if they sell long enough will have a few bad feedbacks. Usually it's because their requirements weren't specific enough and required "tuning" a bit to suit the gun or state of the buyer... or sometimes a flaw that was overlooked by the seller and turned into a big deal buy the buyer. A good seller takes guns apart and inspects them closely, and discloses every flaw in the description.
Some sellers have lots of bad feedback... you wonder how anyone is even willing to buy from them. It's a mystery.
Read the requirements directions of the seller thoroughly. If he has unique payment, shipping or FFL specific requirements that you don't agree with or don't understand, contact him via the link to adjust or verify requirements.
If you blindly buy the gun, then something about the auction doesn't suit you which was in print, and there's an argument... it's on you.
Payment is usually with a USPS MO... they can be verified for authenticity on-line instantly. The shipping and receiving GSs should be quite familiar with the exchange of FFLs... so just follow their individual requirements and you're good to go.
Shoulder Drive Nicholson Club