replacement Roamio Plus and old hard drive

I've had problems with my Roamio Plus recently (pixelation issues, stuttering, four blinking lights, numerous auto reboots) and the box is going to be replaced. My question is: can I replace the hard drive that's in the current unit into the new box and expect it to work without erasing the entire drive?

I'm in the process of offloading all the shows onto an external hard drive via an iMac using kttmg since I suspect the answer is that the drive will be erased.

Thanks in advance,