Connie, I picked up a Two Spools for $30 and then watched one sell for around $600 on ebay. I think it all depends on how badly one wants one, but right now most machines aren't selling very high.
You should keep it, learn to sew with it, and make a couple of quilts with it. And then if you no longer wish to be the steward of the machine, then send it on to the next.
The Two Spools has a perfect 1/4" foot for sewing. To remove the can insert you will need to pull towards you gently on the can to remove. The tip of the can has a spring loaded pin that helps keep the can in place. This pin can be adjusted.
Google threading a National or Eldredge machine, and Two Spools. If you need more help, I will try to help you.