Hi you can try this carefully,very carefully.
Disconnect the linkage from the gearbox,take the 5th gear cover off the back of the gearbox (green cover in the inner wheel arch with 3 13mm bolts holding it on).
Get a copper or brass drift put it against the end of the shaft not on the teeth and gently tap with a hammer see if this will work if not you need to strip fifth gear down and re assemble in the correct way.
Richard
rbtransmissions@aol.com
Richard
June 2007