U really need to back up: that's a fact.
so what is the best way? I suggest you read :
the tivoinside crash course
The Whole Hacking The TiVo FAQ
the first one got it's info almost for 80% from the second one. You still have to do some thinking your self-)
As soon as tiger's mfstool is being relaised the this would be the best way (in my humble opinion) fast and small and backs up from and linux version. Other back up progs need special disks like Dylan or madtivo. i suggest you start looking for the boot cd. I found that easy to use. ( find it, burn , boot it-))
anyway: do extensive reading befor you start.
It's not the fact that yyou make mistakes that worries me, but the destructive size does