I found a garage that did the brakes for a few hundred less than the Midas estimate. Picked up the truck today and boy does it feel good to not have to drive around with an automatic emergency brake locked on the front wheels. The mechanic said the ABS was a rear-only system activated by a lever to prevent locking up when the load on the rear axle is lightened. Still no clue on what, if anything, the 'un-lock' button is for. I'm replacing the P/S and serpentine belts tomorrow.

Too bad about your truck- is it getting cold feet before the pipeline run? How much damage can you do to the P/S system by running it low on fluid? At least you have a backup vehicle...