"My design is a combination of low voltage analog input and high power digital amplifiers. I would like to create a separate ground plane for my analog section. Will this work? What problems will I encounter?"
ANSWER: It is not advisable to split the ground plane in a system containing a digital amplifier (or in most systems). While some issues of switching noise can be solved by splitting the ground plane, EMC is usually adversely effected.
If it is necessary to create a separate ground plane for the analog section, I suggest that you do it with an "island". An "island" is a ground plane that is isolated from the main power ground plane but is completely surrounded by the main power ground plane. Of course, the island should be returned to the main ground with a resistor or ferrite bead.