First off all, you may want to ask around on this forum:
Ranger ForumsSecondly, I'd take the tranny to a Ford (or possibly even a Mazda) dealership and have them do a post-mortem on the tranny. If the Tranny siezed up because of the wrong fluid, you should be able to examine the fluid to determine if that was the true cause. Mazda makes good parts, I find it hard to believe that both trannies would die in the same manner so quickly after leaving their shop.
I would also double check the use of MERCON ATF fluid in a manual transmission. I've never heard of that really (btw, is yours a 4x4, or is it a standard rear wheel drive, that might have something to do with it). You'll also have to prove that they used gear oil instead of ATF, if what you need really is Mercon ATF. I hope they're were dumb enough to mark the type of fluid used on the receipt!!! Good luck!
And yes, mechanic shops are notorious for incompetency and criminal negligence. I used to hangout with this mechanic guy who boasted about how easy it was to rip people off. That's why I've been doing my own repairs on my car as of late, I can't stand that kind of {bleep}.
Oh, and if they refuse to replace your tranny at no cost, be sure to throw a molotov {bleep}tail through their front window. ;-)
- Mike