"without data" would mean $null for the data value, but you might as well put a value to make it easier to $hget like you did above. 1 is a good choice, as is something like $true. Of course, you could also put the nickname as the data field, that way you could do reverse lookups (reverse lookups are done with $hfind)... this is probably required by your script later on anyway.
Converting a text file depends on what your text file format is like... since text is just text-- you need to define some format to be able to parse it into item / data.
