Hacking the tivo involves 2 main, necessary steps
1) bypassing the code in the kernel (initrd, actually) that deletes any foreign files on the tivo root... not sure if 1.3 had this code or not
2) modifying the boot process such that you have some sort of access (telnet, serial bash).
Without doing at least those 2 steps (1 step if your s/w version doesn't reject foreign code), your tivo isn't hacked, and you can't do anything to/with it other than what the tivo standardly allows.
the line to start serial bash is something like:
/bin/bash --login </dev/ttyS2 &>/dev/ttyS2 &
... if you haven't added that code to a file on your tivo (test.conf, rc.sysinit, rc.sysinit.author) then you won't have access to serial bash
As I said earlier, you really should be looking for a tivo hacking guide (my knowledge of old series1 boxes is a bit spotty)... there are a number of old ones out there
edit: for the pedantic among you, yes, you could technically hack a tivo, and add something like TWP WITHOUT enabling either telnet or bash, but what would be the point... you'd be unable to make many changes, and it's almost no extra effort to make sure you have the ability to get to bash somehow