jimtx, good questions. We don't yet know if the MCAS was required for certification of the Max or if it was accepted as an "add-on" due changes in engine size, weight & pylon mount, and as you ask, what the MEL limitations are, if any.
AW&ST highlights an article today entitled,
"Lion Air Probe Expands to 737 MAX Design, Pilot Training" by (Sean Broderick and Guy Norris), states in part:
The directive points operators to existing runaway-trim procedures in the FCOM and quick reference handbook (QRH). If the runaway continues when the autopilot is disengaged—which would be the case if the MCAS is moving the stabilizers—pilots are to flip “cutout switches,” just as on the 737 Next-Generation (NG). As a last resort, pilots are told to “grasp and hold” the stabilizer trim wheel. The FAA has not ordered any changes to how pilots are trained or how the MCAS operates.