The speed and ref sensors are sealed units - I don't think spilling coolant on them would have any effect. Conceivably if the plug end where the wires leave the sensor was loose-fitting, maybe coolant could get in there and cause a short, but that's gotta be a long shot.
Like Rasta said, you can check your coil firing with a timing light, or if you don't have one, simply pull a plug wire, insert a screw driver and hold it close to a gound, then gave someone crank the engine over and see if you get a spark.
The O2 sensor just changes the fuel air mixture when the engine's cold. It would still run if it was non-functional; just badly until the car warmed up.
Have you looked at Clark's troubleshooting section? It's really helpful:
Troubleshooting - Engine
When you did your clutch, I assume you dismounted your speed and ref sensors. Did you pull out each sensor, or did you just take off the bracket? If you pulled off the bracket (with both sensors at the same time) you'll need to re-gap the sensors - and that would cause the problems you're having.