To drain or not to drain

I have a 2005 buick lasabre that my grandma has
owned for 3 years. It has been shifting real hard
going into 2nd gear. And kicks real hard when you
go from reverse to drive. My grandma informed me
a few days ago she has had the car for 3 almost 4
years and has never had the transmisson flushed
and has never changed the filter and gasket. The
car now has 200,289 miles on it. Will it cause me
issues to change the filter since it has been so
long?