1. The price is very high. For a used Encore, I would pay no more than $275 for a blue frame, $175 for the barrel and $125 for the thumb hole stock.
2. I'm not sure what you mean by accurate as different people's criteria for accurate can differ quite a bit. I also have no experience with EABCO barrels.
3. Rub marks on the barrel are normal irrespective of what barrel you use.
4. If it has a hanger bar, there will be a bar screwed on to the barrel and the forend will be screwed on to the bar. If there is no hanger bar, the forend screws directly on to the barrel.
5. Empty cases are extracted.
6. Velocity will probably drop 15 to 30 fps per inch of barrel you remove. Fear not, however, as Encore 22-250 handgun barrels are available and people seem happy with them.