Check Engine and Air Bag lights

I have a 97 Blazer, 160K miles.  The "Check Engine" light has been coming on and off for about 2 years.  Recently, the air bag light has blinked on and off a few times.  Noticed it running rather rough lately and idleing about 6-700rpm.  Took it to AAmco and the put the code reader on it.  It said misfire.  Found a spark plug wire that was suspect, so I replaced all 6 wires.  Still getting a "Check Engine" light, but slightly more intermittent.  Had tune-up performed about 6 months ago, but it still ran like crap and the "Check Engine" light was still on.  Recently, the engine has died while driving a couple of times.  On 2 occassions, it just blinked and restarted.  Could I have a bad plug?  The plugs are sure a pain to change on this Blazer.
Any ideas or suggestions?

My first recommendation would be to get the exact codes (Pxxxx) and list them here.  

Only one plug is really a pain..

But do you know what exactly was done with this 'tune-up'?  Also have your battery checked at Advance or Autozone.  Varying voltages can trip the air bag light.  Also important to note, you're driving a 97, and its 2008, which means unless your blazer has been in an accident, it's time to replace your air bag.  You should have your dealer service your air bag, and that might correct whatevers causing the light to go off.