The other day I did something stupid when I changed the driver's side head light. when I went to put the battery back in I connected the terminals backwards.
(yes I know stupid I've been kicking myself all weekend)

The car starts fine and I don't have a check engine light. but now my after market stereo wont turn on, I hope that is just an inline fuse issue but my hopes for that are low I think it's dead.

my main concern is I just had it tested for emissions and it gets a not ready error. They gave me some instructions on how to reset it by driving in certain patterns (idle for 2 mins, acclerate to this speed, crusie at this speed ..... ect)

What are the chances I killed my ECU or some other important but over priced electronics?

and if so how hard is it to replace an ecu. I've heard it's not really that hard.

And I'm mad that I ran over a Tire when I could have avoided it. Rips up the the Boots and Tires. Makes a horrible noise. So did that Cat (IMG:style_emoticons/default/innocent.gif)

I'd get a new ECU and just put it in yourself. US Fidelis says it cost $2500 or more! (IMG:style_emoticons/default/00000732.gif)

You will need to check all your fuses in both fuse boxs. I'm sure you have blown out at least one. When you reversed the polarity it drained the ecm of all memory, You will have to drive it enough to relearn the ecm and complete the drive cycles required to pass an insp. I doubt you damaged the ecm, there are fuses to protect it from this sort of thing.

thanks for the help. The alternator died on the way home last night. I'm getting that fixed today. I'll check all the fuses when I get it back.