Steering rack removal is detailed in the engine removal instructions here: https://www.mtwc.co.uk/wp-content/uploads/2018/01/MY-ENGINE-REMOVAL-PROCEDURE.pdf I found that the clue about the best position for the rack for actual removal was very useful, you could waste a lot of time without knowing that. Having never replaced just the starter motor, I cannot help with that. Please let us know what you found when it's all done.