I used the install method as outlined here http://basshead.wordpress.com/2010/04/04/snow-leopard-on-acer-aspire-one-aoa150zg5/ with my Install DVD (on a 16gb thumb drive)It depends a lot on the install method you used. If you installed from a normal legit/unhacked cd then you should be ok, might have to update a kext or two.
Excuse me while I first investigate sleepenabler!Sleepenabler.kext will cause a crash if it's not the right version (corresponding to your Mac OS X version), so if you have Sleepenabler, remove it before updating, then just get the latest one after updating to 10.6.4.
That's the only issue otherwise your update will go fine!
I'd love to be able to get the built in wireless to work.