The GameBoy Player basically turns your GameCube into a GBA. In the future, it might be able to be used to provide an alternative method of GBA/GCN connectivity, but for now, and for games like Metroid Prime and Fusion that have already been made, you still need a GameCube, a GBA, and a link cable.
For your situation, this is probably the best solution:
Get a GameBoy Player.
Play Metroid Fusion on the TV to your hearts content.
Beat Metroid Fusion.
Get your hands on a GameBoy Advance and a link cable.
Put Fusion into the GBA, and Prime into the GameCube.
Spend about 2 seconds worrying that you're not getting the light just perfect to see the menus on the GBA screen perfectly.
Unlock stuff.
Give the GBA back to your friend, or put it back in the closet, or whatever.
Play around with bonus stuff in Prime, or put Fusion back into your Cube and play it more.