Dropping the lowers, draining then replacing the lubrication fluid, giving the seals a quick clean and relubing the foam rings takes 10 minutes when you know what you are doing. There is a video here on Mojo which is what I think you want to do (and have probably done before by the sounds of it).
Servicing a FIT damper is something I looked in to but seems to be a massive PITA and best left to the competent/ professionals!
One problem I had with these forks is the lubrication fluid seeping in to the air chamber so I had to regularly let all the air out of the fork whereby the lubrication fluid would also come out, then replace the air and replace the fluid in the lowers. Because of this a lowers service was something I got quite quick at doing!
I suspect the oli volumes you want start from models 49 onwards (start of the 2013 forks) here but without knowing what fork you have it is impossible to say exactly which model number refers to what you need!