The header/footer are injected above/below whatever gcode you import on Carvey, so you don’t need to add any of it manually. All you need in the gcode file, is the code to make the cuts, and it must conform to the spec I linked above
Only the following commands can be in your gcode file:
G0, G1, G4, G17, G20, G21, G40, G54, G61, G90, G94
M0, M1, M2, M3, M4, M5, M6, M7, M8, M9, M30
If your file has anything other than the above, it will get rejected.