Just so you know, the XBox 360 does support 1080p over component. Now, there could be an issue specifically with using the HD DVD drive, which I am not sure about, but I do think I remember hearing something about that in the past.
As for your game saves, look into getting a hard drive adapter. It is called the Xbox 360 connectivity kit, and allows you to hook your 360 hard drive to your computer with a sata cable. There are different ones available, do a search on ebay for xbox 360 connectivity kit or xbox 360 hdd adapter. You can then use a program called Xplorer360, it can be found at xbox-scene.com. I don't have enough posts to leave a link, but if you want a link to the specific page for the program, just send me a pm.
You should be able to backup your hard drive, then copy the data to your new hard drive when you get it.