The linkage has two rose joints that are threaded to adjust the angle. If it is way out you could probably move it onto the next spline where it clamps onto the shaft. There are fine wire clip things that you have to remove to pop the rose joints apart. If you have a fiddle you should work out how they work, but you push the sticking out bit and rotate about a half turn then pull them in a perpendicular direction. Once they are removed you can pull the joint apart to remove the linkage. You then turn the threaded sockets to get the lever at the required angle then push the joints together and reinstate the clips. It is a fiddle first time you do it. Give everything a good clean and a little grease and it should improve your gear change too. You may come across some little foam washers to keep shite out of the joints, but hey will probably be long gone!