86 skyline hatch

gday.....my skyline started shaking recently, it feels like the handbrake is on....i went to a mechanic and he said it most probably is the universal joint and tall shaft. he also told me that if the car was a year newer he could fix it, he said he'd have to send the tall shaft and unit away to get fixed, he said that the u joints are no longer available to get, it just needs to be paired........i never understood how it can be repaired....does it need to be greased or something? thank you if you can help