You don't need it. Just enter your info on PayPal, no need for an account.
Unless, of course, you need the PayPal because you can't use a credit card.
My parents dont use credit, and I was recently drained of all the money in my bank account. I also spent all the money in my wallet on loving super mario sunshine and a memory card. and i spent 4 more dollars on a damn bullstuff refurbish fee for trading in my game. I say its bullstuff becuase I bought a used game which wont allow my to play the first 3 levels on a difficulty higher than 2.
I swear man, I am never trading in anything at gamestop ever again.