First off, I know basically nothing about cars, so I'm sorry if I say all of this wrong, and I am further more sorry if this is the wrong place.

I have an 02 miata with 75k miles. It's making this awful grinding noise in the rear, so I took it in.

I was told by this mechanic that I had to replace my rear pads, rotors, and calipers. I called around to find cheaper parts than he had, and I was then told by a few people that I actually only should have to replace the damaged caliper (I was told by the original mechanic that only one caliper was DAMAGED, but he said I had to replace both or it'd cause a 'pulling effect'. Later, people told me that the calipers have adjusters on it, so that shouldn't happen)

So I called a japanese, mostly miata, specialty place. The guy refuses to let me bring in outside parts, makes sense, and that's ok, but he told me that there is a specific way to change a miata caliper, something about some part or some wrench or tool that shouldn't be used or it can further damage future breaks?

I was just wondering for some insight as to what he might be talking about. I have a family friend who works on cars a lot, and he'd be willing to change it all for me for much cheaper I'm sure, but I don't want to ask that of him when I don't even know what makes it different compared to other cars?