I don't know how to get the stem off, after taking the handle off and the plate off, there is another piece that has a little screw to right,does that somehow com off and if yes how ?

I believe Harden is a model name for a brand made by Symmons. This should be your spindle or stem Symmons/Harden TA-10H Spindle - Locke Plumbing (http://www.lockeplumbing.com/detail.asp?c=Faucet%20Parts%20S%20through%20T&s=Symmons&s2=&sku=SYM-TA-10H&r1=&r2=&r3=) Once the packing nut is removed have you tried turning the stem counterclockwise?