removing the gear box does not damage the clutch in the slightist, the clutch itself is protected by the pressure plate which itself is sturdy. To damage the clutch, you must be a amateur or very clumbsy, but like said if gear box is being removed you can take the clutch off to visually check it, if the clutch was perfectly fine prior to removal you can give the new clutch a miss, but id recommend having it changed, last thing ud want is to have to have it taken out again 6 months down the line due to worn clutch