I bought my first deuce from a private seller. I had no deuce experience, although I was an experienced wrench turner with many years of experience in the muscle car hobby.
I got to go look at the truck, drive it and talk to an experienced owner about the vehicle. Luckily the person I dealt with was extremely honest and not a "used car salesman". I also got a tidy title handed to me, making registration much easier.
I have bought deuces from GL since then, but only because I already have a good deuce and a towbar. If it's a piece of junk with a blown engine, I will towbar it home. And you won't know what it is until you get to it and start trying to prep it for the drive home.
Now, if you buy it from a private owner, you can expect to pay more. How much more is a more difficult question to answer. The person who bought it from GL took all the risk of it being a junker. They got it home and theoretically, fixed whatever was necessary so that you could test drive it.
Now, if you are going to pay private owner prices, I'd expect something to have been done to it. All the trucks clintogf have sold have been serviced with fresh oil changes and all the filters swapped, the entire truck was greased, all the driveline bolts checked for tightness, brakes adjusted, all fluid levels checked, etc. Clean Ga. titles, etc. Basically a ready to run truck.
Nothing wrong with paying a retail price (I've done it) but make sure you are getting retail product for the price.