silly question as i started with an airbag light on, then engine management light came on at the same time that i started missfiring. Have you checked spark plugs and leads. may be nothing but worth a look?

Check the alternator output - if it's voltage regulator has failed it will output a random voltage to various parts of the car - possibly blowing fuses or burning out parts of the circuitry (like the coil pack you replaced) ... check that coil pack for resistance at the two pins entering it, and across the two outlets (as they are linked together) to see what results you get - if you get no resistance, then it's likely the coil pack has burnt out 

It may be expensive, but it's a "combination of errors" caused by one part - the Alternator.  It's rare that the alternator will go in a car that's done less than 80K miles - even on really old cars.

It's the first time I've heard or read of this fault on any Accent, so I think it's a bit of a "freak" occurance as normally when alternators fail it either just fries the battery, or fails to charge it.  A simple test with a multimeter across the battery terminals will help to diagnose an alternator failure (over 14 volts = voltage regulator on alternator is damaged ... less than 12 volts = alternator coils have failed).

I am surprised that the alternator managed to fry the ECU as it would have to have gone through the ECU fuse to do so.

I'm glad to hear you've eventually got it sorted , but sorry to hear it cost so much