1999 Vortec 5.7s (alot of questions)

I am trying to diagnose a Misfire Cyln4 304 error that is driving me nuts. I want to find out if the tuner might help me find out the problem as well as tune up my vehicles.

I have a 1999 Suburban 1500 5.7(R) vortec as well as a 1999 C2500 with a 5.7(R) Vortec.

I have changed over the Suburban from the Central point injection to the new Multi-point injection which helped the engine a ton....a mod I HIGHLY recommend!

What I would like to know:

1. can the tuner help me diagnose the problem.

2. Let me tune the gas delivery to optimize the mileage of the vehicles

3. Tune the transmission so I get better shift point and firmness

4. are there "standard" parameter files or numbers that people have developed that I can plug in my trucks?

What else can I tinker with in these engines to get them to run better and get better mileage.

One last thing, I was thinking about converting the belt driven fan to an electric one but need to find out if I can use/program the ECM to turn on and off the fans (for temp and for A/C)

I know this is a lot to ask but I don't know where else to start.

Thanks!!!