yes
there are a number of things the ultrasound radiation accomplishes; in biochem, we primarily exploit its ability to break open cells, releasing components into solution. however, it's also used to homogenize solutions, i.e. creating emulsions from two immiscible phases.
for this reason, you wouldn't want to use a probe to break up emulsions, it would just create more emulsion (an ultrasonic bath might work to break them up though).
and yes, the solution does tend to get warm after a few minutes of sonicating
after sonicating the plant material, you'd filter it and proceed with the extraction as you normally would. you just replace several hours of boiling or simmering with a few minutes of sonication.