If by learning by mistake you mean waste money and not solve the problem, I will NEVER condone telling somebody to do so.
The computer doesn't "just tell you what it thinks is wrong". It tells you error codes based on problems with sensor readings fed to it. If you actually follow the steps to resolve the problem, you will repair an issue. Your mistake (so far) is simply replacing parts based on the codes rather than finding out why they were set. The computer didn't tell you to replace all those parts. You interpreted that because you didn't take the time to learn how the system works.
You don't need fancy tools to do this. A $5 volt meter from Harbor Freight is all you need to run these tests on an '86. On the OP's '88, all you need is a metal paperclip. Pretty sure he won't have to go to a shop to locate one.
As an example, my '94 2.3 has been throwing three codes since I purchased it. 223, 224, and 172. From memory, 223 is coil primary failure, 224 is loss of dual plug inhibit, and 172 is a lean code. Instead of just replacing the coil pack, I used a meter to verify resistance between the coil packs and the ignition module, between the ignition module and the computer, and the integrity of the coil packs themselves. Between that and a few other tests I pulled from the manual, I was able to determine that the ignition module was the most likely cause. I pulled it, took it in and had it tested, and after confirming it was indeed broken, replaced it with another from a local junkyard that tested clean and cost $40. That solved the first two codes. For the lean code, I checked the functionality of the PCV, ran a cylinder balance test, and finally directly monitored the output voltage of the O2 sensor. Once I'd confirmed that it wasn't producing any voltage, I purchased a new one and swapped it out in about ten minutes.
None of these tests took a particularly long time. They just took a little legwork to find out the steps needed to locate the exact cause of the problem. Once I'd done that, I knew EXACTLY what was causing the problem and was able to repair it right the first time without wasting a cent on the wrong part and with the satisfaction of having repaired it myself. The tools for you to do the same thing are available in your local WalMart (volt meter) and public library (Mitchell manual). Take the time to learn how to fix these problems instead of shotgunning parts at it in hopes that you might win the lottery.
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