98 Rodeo ABS issue

Yesterday I took my 98 Rodeo in to have the range sensor replaced. While I was there I had them perform the recall on the ABS module from last year. I wasn't having a problem with my brakes or ABS system before this but now my ABS light comes on when I get up to 60 MPH and twice I've had my brakes 'give away' a little while sitting at a red light. When I called the dealer they insist that nothing they did as part of the recall would cause this and that it is just a coincidence that I'm having these problems immediately after they replaced the ABS module. They told me to bring the truck back in if the problem continued. Which is fine except that they want to charge me for the repairs since they think they didn't do it. I'm having a lot of trouble believeing that this is pure coincidence and I since I don't know a lot about this I wanted to get your thoughts on it and some info on the ABS module and what it does exactly so when I go back I can be a little more prepared.

Thanks for you help!

Brakes that "give way" while stopping is the feeling you get when ABS activates. The pedal basically goes to the floor. YOu may have a bad/dirty wheel speed sensor. Your ABS can activate when braking on a bumpy surface (common on the 1998+). Better shock absorbers will help this.
G/luck
Joel