When you accelerate hard the gearstick will move, as the engine moves in teh bay, a buggered mount means the gearbox end of the engine moves more, and hence the gearstick moves.
Bog bone is easy in theory, last one i changed on a 16v rewquired about an hour trying to cut the bolt off wiht a hack saw, cus i had left my grinder at home

, and then it took a serious moutn of effort to get teh bolt out cus the downpipe was in the way, after that it was a piece of piss