Question about OS install after HDD Wipe

I just recently bought a new 15" rMBP so I'm recycling my old 17" mbp via Apple's website. Now that I have everything backed up and transferred, I did a 7x erase of the 17" HDD. Once it was done I figured I needed to reinstall the OS.

1. Do you think reinstalling the OS is necessary?

2. If it is, how do I set it up without Registering the computer under my information?

I'm using PowerOn as the recycle and credit service so if anyone has done this before please let me know.

simsaladimbamba said:

Reinstalling is not necessary, but nice for the buyer.
Once the installation is finished, you come to the registration part and Setup Assistant (where you can copy data from a backup or other Mac), that is when you shut down the computer via holding down the power button.

If you have Mac OS X 10.5 Leopard or Mac OS X 10.6 Snow Leopard, that will work, I have not tested it with Mac OS X 10.7 Lion or OS X 10.8 Mountain Lion.

Mac 101: Preparing your old Mac for sale or recycling

Click to expand...

Cool that's exactly what I did but I figured I'd go ahead and ask just to see what everyone had to say.
Cheers!