Cloudiness on oil bath hubs on the older Rangers is actually normal. It only takes a bit of condensation from the heat and cool cycle of unloading at the lake to create enough condensation for the oil to turn cloudy. That’s why they went to black hubs so you couldn’t see that in later years.
As far as whether to disregard oil or not, it’s an ongoing debate by many. Mine is a 2002, and have never had an issue and I put a fair bit of miles on.
That said, I also had to have an axle straightened at Bee Line Sports near St. Cloud and they do a TON of boat trailers. They highly encouraged me to switch mine to grease since they have seen a fair number of failures. The seals apparently aren’t always perfect and can let the oil out at some point. They also said nothing special to do to switch. Take it apart, get all the oil out with carb cleaner or whatever, then just repack with grease. Do this every one or two years depending on miles driven.
I’m still rolling with my oil bath for now, if I start to see issues I’ll switch.