You don't always need new bearings, it is sometimes possible to fit a shorter wedding band, in the same way as you adjust to preload an any other taper roller.
Some claim to have shortened their existing band by careful honing on an oil stone or similar but I have never tried.
Hub should be heated to remove bearings.
One simple of way of checking the preload on the bearings , with the wheel clear of the pavement, is slacken both axle clamps and then carefully torque up the nut on the end of the axle.
You should just start to feel the tension on the bearing at 20 ft/lbs if you attempt to move the rim.
Then you tighten the axle clamps, nut side first, pump the forks then tighten the other side before finally checking the tension on the axle nut.
There is a factory tool and other methods a thou or two difference in preload wont make a huge difference to anything.