A simple wipe cache/dalvik cache and install this should be it. If you want clean install, wipe data, format system, and cache, then install.
Recommended alternate kernel here
Slim_ICS_v2.9 - Stable?[*]Weather Panel Added[*]Few more mods in ASS - Lockscreen Wallpaper doesn't work yet[*]Picasa and chrome sync adapter with gallery google in base[*]Latest sync with AOSP sources as always[/LIST]
Upgrading from 2.8, Format System might be required for SGS2 users. Flash 2.9 Base and your device essentials
Slim ICS 2.9
Slim ICS 2.8 - Stable