Yes the stores do it, it does void Sony's original warranty but the stores offer their own warranty services. Also, accredited sony technicians here themselves perform modchip applications for a fee.
I ordered a mod chip that supposedly shipped on the 18th of December. Still don't have it. So please, I urge you, DO NOT buy from mod-chip.com. They don't even respond to emails promptly, still waiting on a response from last week.
@KoGM777: If you read what I said here https://www.romulation.org/forum/index.php/topic,12969.0.html, you'd know that it's not really that great, it's more like a double edged sword.