IIRC, the software is ~$80, and then you need the correct definition file ($EE, I think), which is another $20. 
As for the harness, I too wonder why folks pay the ridiculous $$$ for the aftermarket harnesses...... 
Don't forget to download freescan and get a connector from Andrew (links on Tunercat's site). 
Also, the OBDI DLC connector can be grabbed from any GM OBDI car at the JY.  I got mine from a cavalier. 
  
Tim 
{edit}Tuner software is $69.95 and the definition file is $19.95