It IS a walk in the park. I got mine across the border and didn't even have to show them PROOF I bought it (no bill of sale, title, etc.)
I did have all that info, but they never asked for it. I did a ton of research on it, and had all these forms I thought I needed, but it turns out all the sources I had must have been out-of-date. They just need a letter from the manufacturer that says it complies with US emissions. That'* ALL you need. I didn't have one of those either, I just said the label under the hood said it complied.
EDIT: Are you picking it up in person and driving it back? That'* what I did. I did not get a shipper. I don't know much about that part.