Got this nice 99 Fatboy last fall...been redoing things little by little. Has 50 k miles on it. Now time to replace / verify fork oil...fact is I hear a spring moving around in there a bit when I bounce bike up and down so I have a feeling on or both forks have little or no oil! Rides fine though so not sure.
Is it as simple as jacking bike up and dropping oil out the bottom and removing caps and putting in new oil? Or are there other pitfalls .
Do I need to buy some seals etc first? Hope I don't find rusted springs....

 

Simple process as you described, not sure if the springs are held down by the caps on your forks, so be careful when removing them (follow the service manual). Consider a set of new springs, the ones in the bike have been holding the front of the bike up for 15 years...

I have been happy with Progressive springs, they were less than 100 bucks I think...

If you don`t have oil leaking out, your seals are fine.