A good time to check the manual transmission fluid is when the engine oil is changed. However, the fluid in the manual transmission does not require changing.
Because this operation can be a little difficult, you may choose to have this done at your GM dealer/retailer service department.
If doing it yourself, be sure to follow all the instructions here, or there could be a false reading.
Notice: Too much or too little fluid can damage your transmission. Too little fluid could cause the transmission to overheat. Be sure to get an accurate reading if you check your transmission fluid.
To check the fluid:
Refer to the Maintenance Schedule to determine what kind of fluid to use. See Recommended Fluids and Lubricants.