Negotiating Liens against the property

[Nick D.]

Have a house under contract and Seller has medical & credit card liens against the property. Can someone help break down the steps as to confirming the all of the liens against the properties 

Also when i call to negotiate these liens, does the seller need to be on the phone or can I get a power of attorney notice and do this.

I know the liens in second position on a preforclosure property can be handled, Im just unsure of the steps needed and who I need to call for each of these liens.