A few years back my mast broke after several weeks of screeching. Tri-point gladly replaced the mast for $113. However, the mast was still noisy. They told me it was normal. Slightly over a year later the mast broke again. This time I fixed it myself. Bought the mast from Mazdatrix for $41. Paid $10 too much, but was able to order online. Downloaded a how to from the following page: http://www.rx7turboturbo.com/robrobi...ce_antenna.htm

The how to is for a second gen, but it worked well. You do have to be careful removing the interior plastic, because it easy to break the fasteners. Once the motor was open I cleaned out all the debris that was probably responsible for the premature mast deaths. I also put extra grease on everything. It took an hour to replace, because I was being extra careful and I didn't have the best tools.

A few days later the mast started making some noise. I raised the antenna and sprayed it with graphite lubricant and went for a drive. The noise was gone. Occasionally the mast will start squeaking, but a spray of lubricant is the fix.

 

I just replaced the mast in my third gen. Some of the above info was encouraging and helpful; but some info sounded like it was for the wrong car. Here is my two-bits of clarification.
My best wrench for the outside retainer ring was a clip wrench.
I think now that I have done the replace, it seems like it would be possible to do through the right jack cover hole; but I was not about to recycle through the job to prove it.
My words for the access route in a third gen: If you have a Bose snake, remove the right side, bend forward the rear section, with the rug out of the way. Open the tool hatch and remove the jack and crank. Get a good trouble light.
You want to bend the right interior panel in the trunk out of the way a little by a pull and lift from the aft end of that right panel. In order to get it loose, you first have to remove the interior panel that skirts the aft part of the trunk. It is held in place by those darn plastic snaps instead of real fasteners, so remove the cap from the aft window washer bottle, and gently lift and nudge the aft panel out of it's snap holes. Bravo.
Now attack the side panel. Unbolt the metal angle tabs from the trunk floor (10mm socket). There are three of those darn friction plastic fasteners to jimmy; one aft and two just inside the jack hatch door toward the fender. Gently work them out, maybe gently pry with a screw driver if necessary. Now the panel should bend out of the way enough to so even short fat arms can access the mast. Remove the top outside part. unplug the connector (plastic spring latch on one side helps it release easy) and friction pull out the antenna cable wire. Hold the unit so it does not escape, and use a (10mm) socket to remove the ONLY bolt that holds it inside. Don't drop the nut. Remove the mast and unit, it is really much easier than it sounded from the other descriptions.
The unit opens easily, and I DID have pieces in there that I removed. Reassemble. My mast re-inserted fine by placing teeth to the rear of car, insert, and turn of radio. Scared me a little but, one off-on cycle got it full up and down after initially it was not all the way down.
Bravo.