Ideally you'd have the forks vertical at 90 degrees if they are off the bike anyway. If not you can check them on the bike just insure you are taking a measurement from the center of the fork bore.
I'd suggest using Mobile One fully synthetic ATF. Its much cheaper than suspension fluid, is an appropriate viscosity and has been used by shops like MX Tech for years, its a proven performer. If you don't have access to Mobile One then Golden Spectro will do the job for you. Up here Mobile One ATF is a normal stock item at places like Wall Mart.
To set the oil height remove the springs and bottom the forks. The oil height measurement is rider dependent. I'll normally set mine between 125 and 130mm from the top of the fork.
Hope that helps,
David