I ask because EB have a 'no questions asked' 7 day return policy that was international when I worked there.
Other places may offer something similar.
To get your moneys worth I would advise against trade in and instead sell it on eBay where you should be able to get close to retail value for it. If it is still brand spankin new anyway.
And yes you should get a pink (or any colour you wish) DS Lite. But that doesn't mean you shouldn't get a PSP too. Perhaps you may like to look at second hand PSPs? You should be able to check them out for firmware version and motherboard version before purchase.
i got a ta82 mother board psp, but it doens't bother me cause im no really in to home brew, and the only games that interest me for the psp is the tales of series, and maybe others if i bother to look.