Clutch and/or transmission or both problem

Vehicle suddenly stop shifting into first and third and only into second and fourth gears and making loud grinding noise while in neutral with clutch let out. Local mechanic says he cannot determine if the transmission has problems until I pay him $1,000.00 to replace the clutch first. Is there not a way that the transmission could be diagnosed to see if their is also a problem with the transmission before I go to expense of replacing clutch? The vehicle is not worth the cost of fixing both. I am confused, please help. Thanks