I just had my shocks and springs replaced. The mechanic said I should keep the OEM springs in case I want to sell the car. But honestly my car is quite old and I don't think I see myself parting from it. Beside, putting the old spring back on probably doesn't worth the hassle.

So, how can I sell it? ebay or junkyard?

 

Keep them. You won't get much on ebay and even less from a junkyard.