Congratulations on you new to you purchase! I am excited for you!
I lived in Marquette so I know the snow you are in for! I hope to get back there soon.
For my trailer before winter I always:
Wax it,
Check on the roof for any areas needing any marine caulk,
Check the roof to make sure vents etc. are secure,
Check around the
windows for gaps in rubber/caulk,
Check all the bolts on the frame to make sure they are tight,
Steel wool any surface rust on the frame,
Spray the frame with rust preventer and a rust protector.
I never winterize mine so other's can better help you out with that.
Happy Camping!