I lapped my last one, my current one is better.
The one precaution I'd take would be to pull off the fan so you don't get metal dust in it.
Other than that, it's pretty straight forward. Start with 600 or so grit, then work up to 1500 or 2000. Lap on a sheet of glass, & switch to dry sanding on your last grit (AKA 2000 Grit).
Then wash it thoroughly in alcohol to get rid of any dust, let it dry, & re-attach the fan.
[EDIT]billw's
link.[/EDIT]
Viper GTS