right i haven't done it in a while but last time i needed to find something that was no longer on the market place
i went to the transfer licence area and then attempted to start it so i could see my D/L history and then d/led from there. but you might not be able to anymore some people haven't been able to do that.
If you use a data transfer cable, you can keep your save games as well. Not sure if you can save them to mem stick as well. Without though, just re-install your games to new h/d, go to download history and re-download your dlcs and content etc. You can then
also transfer your licenses accross to your new machine.