yes those older units did use dextron so your good there
it's been a while since i've worked on one of these but...
as for the sluggishness to engage when its cold and getting better as it gets hot?
i would service it
change the filter (if it has one)
also pull the sump screen and clean it (located at the base of the case, may even be part of the suction line fitting, it should be a mesh screen at the pick up of the suction line). Also pull any plugs out of the valve sections and see if there are any screens in them and clean them out as well.