Verified answer

You only need the transfer cable when you're transferring from one hard drive to another or from console to console and not taking the drive over to the new 360. For the Arcade with internal memory, all you have to do is hook the hard drive up to it and both the drive and your internal memory will be listed as save devices. You can leave it like this or you can move everything over to your new drive by finding the content on your 360, selecting 'move', and then choosing the hard drive as the destination. You will still be able to use your internal memory as extra save space if needed.

No when i upgraded my arcade with a hard drive, i didnt have to do anything but put it in the top of the xbox. And you could actually move every file on the internal memory to the hard drive if you really wanted to, but that is unnecassary.

Just make sure when it asks you to select a save device that you choose the device that you have the saves on, like i said you could move all your info and game saves to the hard drive just by going in the xbox dashboard under settings then memory.

Well if you find your memory card, just plug in your memory card to his 360, then load the save file from his hard drive then save it again to your memory card. Other wise there is no other way :( That I know of at least unless you have a modded 360 that can use flash drives :P

just pop your old hard drive in unless you really need the 120gig