There is an 'update' option, that you get, once u insert the Card, with the Hack. I think it says do 'Install Firmware 1.1?' (or something like that, I DON'T remember the exact words). You press on the 'Yes' option, and the installation begins. It takes about 5 mins or so to install (I didn't actually time, how long it takes :P ). BTW, you battery has to be FULL, when you insert the card, with the hack. Otherwise, if it stops half-way, you GH2 would be history ;).
Also, when you switch from the shoot to play, again, the same option about Firmware update pops up. You click on the 'No' option, this time (if you did not format your card, Immediately after installing the Hack). It will format your card, and, the hack is not on your card anymore, but, installed, on your GH2.
I doubt whether anyone can notice the quality change on the GH2, with the Hack, by looking at the camera's LCD. If they claim, they do, please sent them, to a good psychiatrist :lol:. Also,Unless you have a Full HD monster of a Monitor, and use software for screen grabs, there is a chance that you might not be able to notice the difference. The FlowMotion Hack handles fast moving action, with a lot of detail (flowing water etc), a little better, than the Original Firmware. And, like all hacks, because of the (much) large file size, coloring and grading would be a tad better.
Congrats