Reboot takes 30 min, video stuttering

I have a Roamio Plus and recently the unit has started to spontaneously reboot. The rebooting process takes on average 30 min. When the TiVo video finally plays, it stutters. Once in the main menu, trying to watch TV usually doesn't work, and playing recorded shows is iffy at best, usually with a lot of stuttering.



I'm guessing this is my HD failing.



I talked to TiVo tech support and they want to RMA the unit. I am pretty computer savvy, so I have no problem fixing the system if it's just the Hd. Just wondering if I'm better off to do that (replace HD myself) or let them send me a whole new (refurb) unit?



Do HD's put into Roamios still need to be prepped?



Also, is there any way to save my existing recordings?



Thanks!