S-tronic = DSG. A3 diesels cling onto their value, perhaps more than GTIs.
i think it's reasonable to expect a straight swap, with the proviso that it's got the S-Line bodykit because early A3s had separate S-Line kits for the exterior and interior, and the exterior kit was basically a spoiler and some 18". the later ones (like mine) had a full bodykit and the "S-Line" was a single pack/trim level.