The timetable changes taking place on 20th May 2018 are the biggest change in a generation.
Whether they are an improvement for you or a deterioration (we suspect more of the latter than the former), for everyone they will be different.
New timetables can be found at at https://www.tpexpress.co.uk/travel-updates/may-2018-timetable-changes/north-route-timetable-2018 (TPE) and https://be803fe5c416e39d38ae-aa21086260d3bd4e072d597fe09c2e80.ssl.cf3.rackcdn.com/images/timetables/2018-05/summer-2018-timetables/Northern-25-booklet-0418-28pp.pdf (Northern).
Print versions of TPE’s timetables now available at Stalybridge & Huddersfield stations, print version of Northern’s timetables not available until 1st June.
Also bear in mind that at Marsden almost all Manchester-bound trains (except for the first morning train on weekdays) will call at platform 2, not platform 3, so allow that little bit of extra time to get there.