I'm not sure if it's even linked in the docs.
I only know about this because cmb posted it here:
http://forum.pfsense.org/index.php/topic,6784.0.html
I'm not sure if in 1.3 the gui solution will just be an implementation of the described procedure in the pdf.
But dont worry about breaking someting when you update to 1.3
1.3 is still more than a year (or even more) away :)