Hi Bird,
Remove the lower spray arm by unscrewing the cap (#34 on the
break down diagram). Remove the filter guard (#36 on the
break down diagram) and the cover (#4 on the
break down diagram). Remove the pump housing filter (#6 on the
break down diagram) and the rinse arm assembly (#7 on the
break down diagram).
Soak all affected parts in white vinegar and brush them, using a soft metal brush.
I do not recommend to remove the upper spray arm - you can damage the retainer.
Assemble it back. Start the regular wash cycle. After the dishwasher filled with water open the door and pour a gallon of white vinegar in and do not restart the cycle for about 12 hours.
Restart the dishwasher and finish the cycle.
Here are the break down diagrams for the Maytag dishwasher
Model MDB5000AWB
Gene.