I need to replace the passenger side front arm with a new one so have tipped the car on the drivers side and have started to remove the things attached to the leg. The issue I have is that the main through bolt. It seems to be stuck fast, as it doesn't want to move at all, but I've not fully dismantled the front suspension. I thought that if the tie rod and nut were removed then the whole unit would come away from the leg, allowing me to replace the leg. Is this right or should I be dismantling the unit before the main bolt can be removed?
Picture for reference:

Any thoughts of this as I'm sure I'm not the first to do this...
Many thanks in advance...