An ECM tune is different than a "chip". A "Chip" upgrade is where you physically remove the chip and replace it with a performance chip. With an ECM re-tune you are actually reprogramming the computer that controls the car (there is no removeable chip). Now, technically all you are doing is changing some values in tables that the computer uses to manage the engine so, in reality, you're not actually changing the programming but changing the data the programming uses. Regardless, most will call it reprogramming anyway. LOL
Understanding that you CAN do this at home, sort of. What happens is you either order a re-tuned ECM and pay a core charge. The ECM is sent out to you and, once you get it, you install it at home by taking the one that is in your car now out and putting the new one in. Then you send your original ECM back to the vendor and he'll refund your core charge. OR, you just take your ECM out, send it to the vendor, he "reprograms" it then sends it back to you to re-install. Problem with this route is while you don't get charged a core charge, you are out a car until you get the ECM back.
Overall it is a great modification, however, retuning the ECM is a tricky thing. There is a different "tune" for each modification you put on your car just about...so a retuned ECM for a stock car wouldn't be optimal for a car with CAI, cat back, and headers. While it would work, having a tune that is set up for those mods is best.
Good news is this vendor can set you up with a tune for any combination of modifications (or no modifications) and program them into an ECM for you. Just be sure to tell him what you have done to the car and what you are planning to do to work out the best option in ECM reprogramming for your particular situation.