3D programs

I am pretty well up to speed with 2D drafting but sorely lacking in
learning a 3D program a buddy is lacking also. I have Rhino and solid
works but have installed neither. I hear and see good things about
Rhino. Does anyone know what an average time in hours is required to
get to a basic working level with Rhino. I am OK with my CAM program
and have a 49" x axis X 49" Y axis X 6"Z axis stepper driven CNC router
under construction. I would like to do Bass Relief on urethane foam for
signs.