Looking for Gearbox, clutch + valve stem seal or guides etc

Hi, im potentially looking for a gearbox and a clutch kit. Im guessing a clutch kit I can source from honda without too much trouble but any suggestions to try for a gearbox? Synchro for 5th is worn and wines in 5th, so unless I can get parts to repair it easier (plus fitting them) I am looking at a new box if possible.
It also used oil, seems to be burning it on one cylinder and from top end. Any advice on this for parts and for doing the job? Many thanks :)