How much would i get for this at a pawn shop?

my 'aunt' and 'uncle' got it for me from either Sears or Kohls, i dont remember which one... but its a solid white gold chain and heart pendant, and half of the heart are real diamonds. we got it on clearance for a bill, but the actual price on it was $475.... i like it, but the chains really thin and dainty, and kinda short, so.... theres this REALLY awesome pawn shop 30 seconds away from my house, and they give really good money there. theres a bass guitar in the showroom i want. i dont know the make and model, but its got blue glitter in the body paint, and its got this white pearl pickguard... i REALLY want this bass, and asap, too, cuz there were a couple kids and their mom looking at it the other day... but its $80... if i pawn my necklace, do you think they'll give me enough money to buy my bass? and mayve even a $20 amp, too? and also, will i get more money if i pawn it, or sell it? cuz if ill get more money for pawning it, ill pawn it, and just never pay them back...