EBS brakes

[72BLKCHEYENNE]

Can someone help?

I have a 99 yukon, my ABS light has been coming on the last couple of days. If the warning light is on when I first start to move the breaks seem to work ok, but if the warning light is off when I first start and I hit the break peddal the pedal is hard and the breaks chatter as if the ABS is trying to work. The warning light then comes on and stays on until I turn the truck off. Can someone shed a little info on this so I don't get riped off when I take the truck to get looked at. This is why I would rather drive my 68 things are just plain and simple they either work or don't work....no electronics

thanks......Rick