The Trek is a 1st class way to do it. If you are financially challenged you can try the do it yourself approach at Hammond Wiki: HammondWiki - Line Out From A Spinet HammondWiki - Line Out From A Hammond Console
Also good advice about staying away from the multipin (usually 5 or 6) tone cabinet Leslie plug. Quite often there is 110VAC on one or more of the pins. DANGEROUS Stuff!!