97 Tahoe won't start. Cranks, has no spark

After pulling into the parking lot at church after a 600 mile snow trip with students, my Tahoe decided to no longer start. I tried jumping, still just made a single loud click. Tried new battery, still made same click. Towed home, cleaned up connections on batter and even replaced starter. Now starter will engage and turn engine over (with decent power) but won't start. I checked ign fuse and what not in hood fuse compartment, they are fine. Pulled the front spark plug wire on either side of engine, put a new plug in and held to a metal part of engine. Did not get any spark on either side. What do I check next? Vehicle was running fine 3 days ago (though I had received a obdII code for O2 sensor stuff, and it smokes, possibly cracked head gasket?).

The O2 Sensor codes were telling you that something was going on in the engine. It's their job.

With the no-spark condition it could be ignition control module, I believe that Auto Zone can test this for you, Ignition coil, Haynes or Chilton Manual should have test procedures.

Have you pulled the distributor cap and checked the rotor ?

Also check the distributor shaft for rotation to make sure gear is not stripped or sheared from shaft.

Check for battery voltage to coil, Haynes or Chilton's Manual.

Sorry I do not have the wiring diagram or procedure available to me at present.

since the vehicle had a bad starter and it was JUMPED it is very possible that the ignition module got damaged at that time...

make sure the distributor has 12volts then replace the module..