I sure don't know how to help, as I don't even know what a sure stitch is. I did just google it, and I thought it was a type of sewing machine, but maybe it is an attachment.
At any rate, I would want to make sure it worked before I bought it. Whoever is selling it ought to be able to demonstrate it, you would think. Have you talked to the seller? Maybe you and a friend could make a lunch date type thing to go look at it. I don't think I would go alone.
Hope you figure out what is best for you.
Dina