Changing tire/gear ratio?

[v30crewcab]

So what are the different ways to change the tire or gear ratio in the computer?
I had BP setup my computer for 3.08 gears as I was trying to get my truck together for the power tour and didn't have time to change gears. now that I want to change to lower ones, what is the solution to changing it in the computer? My friend has hp tuners and it sounds like it will cost $100 for him to get into it, even though its been previously opened? is that correct?
1. hp tuners
2. snapon or matco computer? do they have that option?
3. dealer computer
4.???
5.???