You will not lose any of your recorded shows, even if the Tivo has cable cards changed. You just need to re-run guided setup when your new cable is installed and if any cable cards are needed/changed.
Original S1 (Recycle Heaven)
Series 2 (PLS, sold)
TiVo HD (XL, PLS, "652")
Juliet Basic (4XL, PLS)
The TiVo Apocalypse begins on Sat 2013 Feb 16 00:00 GMT!