My staircase has Mohawk 3/8" laminate wood plank, and I like to remove
the laminate wood and prep the surface to receive carpet.

Here are some pictures of my staircase:
http://www.geocities.com/dchou4u/photopagetan.html

The complex thing about this is that the balusters and newels are
resting directly on the laminate wood treads. So if I remove the
treads, the height will be a little different.

The treads are about 11.5" and the riser are about 5.5".

Do I need to replace the plywood under the laminate surface?
If the plywood is missing the toe, can I glue and screw in a 1/2 round
to create the toe for the treads?

Will a general contractor be able to redo the stairs for me, or do I
need to hire a stairs specalist?

Thanks