I have had the Torque converter changed but still can’t get reverse gear, the mechanic wants to replace the valve block, Where can I buy a reconditioned valve block or solenoids for a 3.0 TD6 Auto?

I am new to this forum and hoping I can pick the brains of someone here about my landy. My 90 has developed a really bad vibration when going above 30mph, whether in low (not very often) or in high the transmission winds itself up, and have to raise the wheels to unwind, the transfer box has...