I have nooooooooo clue on how Efi works. This is why I'm asking. I thought Efi was just a product distributed by dealers on a tool that they install on your truck.
There are several methods of getting an EFI Live tune on your truck. Unlike other "tuners" (Edge, Hypertech, etc.), EFI Live is a software program that allows the tuner (taking about a person/profession this time) to alter the tables and parameters that define how your engine runs. This becomes known as a "tune".
Different tuners use different tuning techniques and strategies to get the result you want for your truck. As such, no two EFI Live tunes are the same. That is why people are so adamant that you choose a tune provider that will give you what you want (if that's a smoke tune - hey, it's a free country, but don't expect to be popular on here).
Since EFI Live is just software, there are several methods of getting the desired tune onto your truck. The first method (and sometimes cheaper, depending on your tuner of choice) is to have the tune installed on your vehicle at the tuner's shop. The tuner will flash the tune onto your truck using the EFI Live software and a V2 Scan/Tune tool. This is probably the method Longhorn was planning on using.
Another method is remote flashing of your vehicle. This is accomplished with the EFI Live AutoCal device. The AutoCal is a smaller device that the tuner provides and you, the end user, use to actually flash the provided tune. The AutoCal can also be used to monitor engine parameters as well as to read and clear codes. Quoting from EFI Live's website: "The end user gains access to the tune, and the ability to data log/read clear codes, but the Tuner retains software permissions."
The third option is to purchase your own V2 Scan/Tune tool. People who choose to do this often want the enhanced scanning capabilities the V2 offers. The V2 can be used in conjunction with a license to create your own tune, or a tuner can provide a tune that you will flash in, just like with the AutoCal. This is the most expensive option, as the V2 is somewhat spendy on its own.
As far as recommending a good tuner, all I can say is to read reviews and do your research. Most people here post their tuner in their signature, which would indicate they are happy with the results they received.