surburban furnace will not light

finally had a chance to check heater again. I have 12 volts to/from sail switch and 12 volts to circuit board . I do not have any voltage coming out of board or any type of voltage on high tension wire. So Board is bad? I disconected high tension wire and the plug on the end of the board . Removed two mounting nuts, but cannot make board clear mounting screws without the big black module on board hitting side of blower cage. Removed one mounting srew on front of blower cannot see others to remove. Any I deas how to disassymble this . Heater is mounted under stove no overhead acess unless stove is pulled . Should the heater be able to be removed thru outside cover.