Power seat issue

[drsrt8]

2001 chevy tahoe LT with full power seats. The bottom slide, tilt and back tilt stopped working. Heater lumbar and side bolsters still work. I have power to the black box but nothing coming out (which is why it does not work). Can i just replace the black box under the seat?

If it can not be replaced is there a manual override to move the seat forward to get the last bolt out to replace the entire bottom rack?

thanks