If you get a coding cable, the registration DIY can be found easily on these boards and the software shouldn't be too tough either (look for coding software, same package). The dealer will overcharge for this, but that's definitely the easier option, especially if you don't already have the $100 coding cable, though that can come in handy for other stuff and future battery replacements too.
'16 Cayman GT4 (delivery pics
Gone but not forgotten:
'11.75 M3 E92 Le Mans | Black Nov w/ Alum | 6MT (owned 5/2011 - 11/2015)