4105 Hydro fluid / filter change

HI , I am new to the sight, looks to be a great sight, Awhile back I bought a 2008 4105 hydro tractor, it now has 280 hrs. the manual says 500 hrs. for a fluid / filter change, I am thinking on doing it now before winter, any opinions on this? don't want to waste money, I bought it with 210 hrs. & it had not been done, you would think it would be a good thing and maybe should have been done earlier than this, also I am running mobile 1 synthetic, what weight do you recommend , like in South Dakota, so it can get nasty cold.
Thanks for any help!