Well there are mechanics, and then there are mechanics.
I would do a compression check, make sure the cam timing is right, ignition timing is right & replace the fuel filter.
Then I would go here http://www.aeu86.org/technical/ae86-manuals/
and download the 4AGE Diagnostics manual.
It looks complicated, but really it isn't. Make sure the throttle position sensor is set properly and follow the various diagnostic charts. You will need a multimeter but they aren't expensive.
These engines are pretty foolproof, as long as the sensors are set correctly and the basics like compression and timing are correct.
ECU's don't fail, neither do coil / igniters. Keep it simple and work through methodically and it will run great.