Junker

I need to replace the springs and oil in my 1989 Venture. I have done many fork overhauls but never on something with air ride. Taking them apart and puting them back to gether is pretty straight forward but refilling the oil has me questioning what I am reading. Can you fill the forks from the top like any other fork or do you need to fill the lower tube through another means? Besides new fork seals is there anything that needs to be changed while I am in there? Thanks Junker