I started as a mechanic and I know the learning curve is steep. Jet / TC is really the only decent software to tune the '99 Suburban. I use TC on mine. The '0411 is reported to be a better computer with a better program but I just keep using the stock one as I don't have time for any extra projects now.

It might be easier if you describe what problem(s) you are trying to solve. If you want to jump into the pool with both feet there are some good resources such as the EFI University products. The "How To Tune and Modify Chevrolet Fuel Injection" is a decent read for the beginning. Greg Banish is an excellent teacher imo and his two books "Engine Management: Advance Tuning" and "Designing and Tuning High-Performance Fuel Injection Systems" both have good information. Although many of the old OBDI discussions can give you basics and descriptions of important functions that are part of OBDII, I think you might find some OBDII related "How to tune" discussions in HPTuners forum, the EFILIve forum, and thridgen.org as well as a number of other sites.