HPTuners is the way to go
my advice is read out your standard tune...then save it in various places (USB, Hardrive etc)
Then after that only change ONE thing at a time, (maybe start with speed limiter) then test the car
As a backup to start with always use the "compare" feature to show you the difference from your OEM tune, this way you can make sure you have not done anything by mistake!!!!
To really get the best from the software you Will need a good wide band AFR meter .........and it's a good idea to hard wire it in to the exhaust system (Left bank if you can.