Yes, if you are on 3.55 ofw, but i use to install qaflag, restart and try the button combo, just to see that its ok.
Dont know if you have to do this...
Install from recovery mode, enter by holding the power button, when it turns off, hold it again, you wil get to peeps, the stop holding the power button.
Rebug 4.70.1 is the latest, Get it from
www.rebug.me
You can spoofe this to use psn, just be sure you install psnpatcher or other homebrew the delete traces of the cfw, this is not 100% secure, but i never been banned with this.
Hope that was helpfull, check out Psx-place.com for tuts and relases
Edit: i install rogero 3.55 v3.7 when i downgrade ps3's, so qaflag, then 3.55 ofw and rebug or others. Remeber, never have a disc in ps3 when updateing!
Edit2: rex is standar and what you wil install when you are on ofw.
Dex is more for advance i think, more patches and stuff, but you can have semi dex on rex, enabled by toolbox. This help for fake savegame and others xmb options

If you are not so in to the ps3 stuff, you shoud read up abit and if you dont have any flasher to save you when you fuck up ( this wil happend, at least it did to me so noe i got eflasher and a few treensy adapters and two progskeets )
Make some flash dumps from toolbox.
Edit3: rebug 4.70.1 is build on 4.70 so you can play games that are up to that fw.
If you wil have psn on rebug, you have to spoof. As said earlyer
