Q1 All 1856 were, in theory, struck as Proofs (Yes I know they weren't but the TPG's had so much trouble separating the Proofs from the Unc that they finally decided to just call ALL of them Proof.) So Net Proof-12 Details Graffiti means that it is a Proof, it has deliberate scratching of something on the surface (graffiti) and because of that if has had its grade reduced to that of a 12 grade coin (the net grade)
Q2. As Sandon says I would also want to see a good image to be able to tell how bad the damage was so I could decide if the had reduced the grade enough or not enough.
Q3. GC's bank is willing to accept checks and/or money orders from them.