You can keep the old box to watch shows.
But there is a charge if you keep it beyond 30 days.
Not sure if it is just a monthly charge for stb or for the entire device.
You will need to disconnect coax from old DVR prior to installing quantum.
Be careful, because if your old DVR happens to lose power, you will no longer be able to use it.
May want to try and reduce the amount recorded or see if some are available on demand before ordering quantum.