if it's just the player, no speakers or anything fancy, spend another $5-10 at walmart for a harness for your car, and then it's just match-up the wires.
off the top of my head, you'll have:
2 purple - one with stripe
2 white - one with stripe
2 green - one with stripe
2 gray - one with stripe
black (ground)
yellow
red
those will be your functionality wires. i believe there's a blue in there for the power antenna, and another blue for amp turn on, but i don't know that a GL has the premium sound, so don't worry about that one. and that may be it, pretty simple, strip the wires, splice them with electric tape, or something more fancy if you've got it
any questions, keep asking...