If the ride is good for you just put the stock weight back in it. Personally i would pull the forks off and check the wear items while you are at it. Plus you can turn them upside down in a drain pan over night to get all the old oil out.
What Frankie said but if you just want to drain and fill , use a cup to measure what you take out. You may need heat to remove the drain screws. A lot of guy use the HD SE fork oil to reduce the bounce of the stock front end.
2010 FLTRX , Stage 1, 13" Madstad, Mono tubes, SuperShox, Heritage style bars. Alpine CDE-HD149BT,Soundstream Picasso Nano Series PN4.520 , 5X7 and 6.5 Infinity Kappa speakers
If I have to explain ,you wouldn't under stand anyway.