It's a good idea to get the model number so you can check to see if it's still being made. There have been a lot of small lathes sold over the years, and just the size is not enough to be sure of what you are looking at. Some have more features than others. A 20 year old model may not have the same features as this years model.
If it is the current model ( G8688 ), and it's used very little, then $300 is not too bad a price.
The 7x12 is similar to the one I have. They are a fun little machine to learn on and can make 6 inch long lights with no problems. The largest part that will clear the saddle is somewhere around 4 inches in diameter.
I think they are a good learning machine simply because they are lower power and hold smaller pieces. When you do stupid stuff and dig in a tool it's not as catastrophic as when you have a 70 pound chuck to act as a flywheel. It will still break tools and can still injure you.
If you get the 7x12 and like it, you will eventually want something bigger. :)
Daniel