[embee]

Oil level is a bit flexible. As long as it covers the holes it will give the same damping effects whatever the level, but the level affects how much air is left above the oil (air gap) which works as a secondary spring as it gets compressed. The bigger the air gap the less stiff the spring effect from compressing it, smaller gap means more pronounced air spring effect.

Set it to whatever is recommended for your model for a start, you can always change it a bit later.

Remember that the oil level is set by removing the spacer and spring, and fully compressing the fork. Held upright (in a vice etc is most practical) you measure the distance from the top of the tube down to the oil. You can use a steel rule or stick etc, various ways to do it. There are tools with an adjustable tube in a bracket which you can sit on top of the fork tube and use a syringe to simply suck out oil until it drops to the set level, they make it easy but are not necessary by any means.

You can usually get a fork oil change from a 1 litre bottle with a little left over, i.e. a bit less than 500ml in each side. It is really annoying when a particular bike needs just over 500ml per side.

Are your new springs the same relaxed length as the old ones? You may need to alter the spacer tubes to suit if they are not. You may also find the sag when you put the bike back on its wheels won't be ideal. With height adjusters in the top caps you can get a reasonable range, but you may need to alter the spacers if you can't get it right.