Answers to a few of your questions can be found here:
http://www.pinwiki.com/wiki/index.php?title=General

First, stop replacing coils unless they measure as bad with a multimeter or show signs of stress or melting. Good coils should show around 4+ ohms, depending on the coil of course. Measure one you know is good then compare that reason to the others. Tri Zone uses several coils that are all the same. I think pretty much all of them are the same except for the flipper coils.

Check the diode orientation on all the coils you have replaced. Power goes to the banded side of the diode.

Check for shorted transistors on the driver board. The quick check is meter on continuity, black lead on the ground strap, red lead touches the metal tab of all the transistors. If you get a beep, the transistor is shorted.

Check that you don't have several or all the coils firing at once when you power on the game. If it is doing this, you may have a blanking issue and need to track down the problem.

What can often happen is:

-A transistor shorts, locks on a coil, and burns it up.
-Driver board is repaired, bad transistor(s) replaced
-Coil is replaced and wired backwards, or coil is not replaced
-Repaired driver board is installed, game is powered on, fuse blows, transistor blows
-You now may be back at step one

You have to take a step back, check everything, double check it, then start again. And Xenon75's advice to check all header pins is also good advice.