TiVo Roamio Plus

First let me say I am brand new to Tivo. I have the Roamio Plus model and I would like to increase my storage. Everything I have read stated not to by the WD EXT HD. So I am looking for a internal replacement drive. I would like to install either a 2TB or 3TB drive. Can someone please tell me what drive to buy and from where? Also since the unit is brand new what happens with my warranty.



Thank You