You might also consider getting a "second opinion". To the best of my knowledge, only the dealership can read the ABS codes (please, someone correct me if I'm wrong), so you're stuck dealing with them, at least for a moment. But you might want to consider bringing it to another Isuzu dealer and asking for a "diagnostic", claiming that you intend to do the work yourself. The diags will cost you about $94, but they have no incentive to lie to you about what they find if they don't think they'll be doing the work. I would do this regardless of whether I am considering using that shop or not because it makes them think you know a thing or two about cars and they are much less likely to try to rip you off.
I'm not saying necessarily that this dealership is trying to con you, but I wouldn't put it past ANY mechanic unless you've had positive dealings with them before. Your ABS light could be any number of things (mine happens to be a $300 speed sensor) so before spending hundreds or even thousands of dollars, I would make sure you know what you're paying for. Plus, this forum is all about helping folks like you and me learn to maintain our own vehicles so we don't have to be at the mercy of the "stealership".
Then again, like others have mentioned, you could always just ignore the light. I've been driving with mine on for months now and it's not doing any harm. However, I suppose you are taking the risk that if you got into a major accident and your braking system was a factor, if it comes out that you failed to maintain the safety equipment on the vehicle you could be found at fault. That's something that I keep rolling around in the back of my head (with all the rocks and junk).
Kyle
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