Crank position sensor is on the front of the engine. On a 1996, the CPS does not affect the running of the engine at all. It is only there to sense misfires and report them.
You did get an LT1 OBD2 code reader, right? Anyone that owns one of these LT powered cars needs to have a good code reader. Even if you're not going to do the wrenching, it'll save you from being rooked by shady mechanics who like to load up the parts cannon and blast away. Once you get one, do the tests I mentioned earlier. The logs will really go a long way towards helping you find what's going on. Sans a reader, there are a few things you can do on your own for under $50 and some time. At the LEAST, you need a way to clear the codes to properly test. Go to Autozone and rent a vacuum gauge, and a compression tester. Since this is isolated to #4, it's probably not fuel pressure related.
Your next step needs to be getting the car home and out of that rip-off artist's shop. You can get the injectors - brand new - for $500 all day long. You can score a set of reconditioned injectors on the 'bay for $200 or less with minimal effort. Pulling the fuel rail and replacing the injectors is a 15 minute job. But you have a lot of bridges to cross before you get to 'injector replacement' time.
Getting to the opti leads on that side of the opti is a pain in the ass otherwise I'd suggest moving some leads around to see if it follows the plug lead. You can buy a cheap spark tester for $15 and make sure that cylinder is getting good spark. Good spark? Move on. Pull the plug out and look at it. Oily? Rings, valve seals, or intake manifold gasket. Good? Move on. Insert compression tester in plug hole. Pull fuse for fuel injection. Pull coil lead. Get in the car, floor it, and turn the key until the engine turns over 6-8 times. Keep the gas pedal floored - throttle blades must be open. Look at what the compression tester says. 160-200 is good. If it's low, piston rings, head gasket, valvetrain. Good? Move on. Plug everything back up and stick the spark plug back in and connect it to the lead. On the pass side of the intake, find the top vac. port and pull the rubber line off and plug the vacuum gauge to it. Go around and start the car. Watch the needle while the car idles - it should be 15# or so. If it pulses a lot, you have a vacuum leak, hole in piston, bad ring, or a collapsed lifter. Given the #4 misfire and that you never mentioned death-rattles or smoke, if you DO have a leak, its probably at the intake manifold at #4. Get some carb cleaner, start the car, and spray it all around the base of the intake - where it meets the head. If the car stumbles or the RPMs increase, its the gasket. If not - move on. (It still COULD be the inner manifold gasket. The plugs would tell you if this was the case. They'd be oily.) Another common source for a vac leak is around the injectors. Spray the carb cleaner around each injector where it goes into the manifold. If the RPM's are affected, you've found a leak.
Test the injector pulse. A noid light is the only safe way to make sure the injector harness is sending the pulse to fire that injector. Harbor Freight has a
set for $40. Hook it up to #4 and start the car. Watch the light and make sure it's stable. Now you've probably done more troubleshooting than any of the mechanics you hired and the only thing you've had to actually wrench on is removing one spark plug.
A quick and easy test you can do is to pull the injector rail and swap injector #4 with injector #2, clear the codes, and see what happens. Pulling the fuel rail sounds hard, but it is stupid easy. My 10 year old daughter could do it. Pull off the home-plate, pull off the 4 bolts, disconnect the rubber line to the fuel pressure regulator, and slowly pry it up - moving around to different points on the rail as you go. Once it is free of the intake, go ahead and turn the key on to run, but do not try to start it. This will pressurize the rail. Let it sit for a few minutes with the key on. Then look at each injector for leaking. Leaks? Bad injector. Replace it. No leaks? Move on. Turn the key off. Disconnect the rubber line to the round canister at the back of the rail. Fuel coming out? Bad regulator. Replace it. No fuel? Move on. Disconnect the leads to the injectors. Get a few rags to catch the fuel that will dump out of the rail when you pull the injector. Pry off the tabs of the injector clips. Pull the injector out of the rail. Swap over to the front most spot (#2). Install is the reverse of removal. I use water on the o-rings to facilitate them sliding back into the intake. Clear the codes and start the car. If P0302 comes up, it's the injector. If P0304 comes back, it's either ignition, injector pulse, or mechanical failure of something in #4
Ideally, you would replace all of the o-rings when you take the injectors out, but for a quick test it is not necessary. If you really wanted to earn your wrenching stripes, you could service all 8 injectors yourself.
The kit for this is $30 and you'd probably have an hour into the job if you were taking beer breaks. I did this over my lunchbreak in my parking garage at work. And I had to wear nice clothes to work...
Any mechanic worth their salt would have conducted every single test I mentioned here because it would have caught 99% of misfire culprits in about 2 hours. Max.