Abs & Brake Warning Lights

I have a 2001 Blazer. Several months ago the ABS & BRAKE warning lights started coming on at the same time. After stopping and shutting off the engine for awhile, they stay off until I have started driving it again. Sometimes within a few blocks, sometimes several miles. I suspect some kind of wheel sensor problem, but don't know what a wheel sensor looks like. I don't know if this is something I should be able to fix relatively easy myself, or if I'll need to take it in to a shop. Anyone else with this type of experience? Also, the brakes are still working fine. I cannot be certain about the ABS system though. Thanks