Just flash through CWM. Make sure to factory reset, wipe cache, wipe dalvik, then install. I think that's more wipes that you need, but it won't hurt.
I've been on the ICS ROMs since about 30 minutes after the first beta was posted. I have only had issues with the TouchStone on the ROMs that include bricked kernel. CM9 alpha 2 is by far the best today. I haven't had a single sleep death or freeze as you describe since I came to alpha 2. And none of the ICS ROMs have given me wifi woes like CM7 did.
Ditto the comment above. You will kick yourself for still using CM7 about 4 seconds after the get into ICS. Its freaking amazing, like having a whole new device.
Sent from my Galaxy S II (i777)
> HTC 8525
> iPhone 3G
> iPhone 3GS (it was a dark time in my life, I was confused)
> Palm Pre
> HTC Aria
> Samsung Captivate
> LG Thrill
> Samsung Focus
> Samsung Galaxy S II (I777)
> HTC One X
> Samsung Galaxy Note II (I317)
+ HP TouchPad