This will put you back on a clean install of stock & you then have another go at custom kernels/roms from there.
You can probably muck around with other methods, but given you say you're 'out of your depth', going back to square one (stock) & proceeding from there would be easiest/least time consuming for you.
Actually, scrub what I said about CM9. Well, kinda. You're using an old build of CM9. Before you do the stock thing as above, download the latest CM9 nightly & flash that in CWM. See if that resolves things before you go back to stock.
Last week I tried to root my Galaxy SII and I stuffed it up a little. Currently I'm running Cyanogen 9 ICS with a CF-Root kernel. It works except that I have no data connectivity or support for the built in SD card. From what I can gather this is a problem with the kernel that I used. In light of this I want to flash back to the stock kernel that came with my phone, but I don't know what it is or how to find out.
So anyway I'm way out of my depth here and would appreciate a little help. Thanks in advanced!
This is the information I have on my "about phone" page:
Model number: GT-I9100
Android Version: 4.0.4
Baseband version: I9100XXLPQ
Kernel Version: 3.0.28-CM-g41e6bf7 codeworkx@cyanogenmod #1 SMP PREEMPT Fri Apr 20 18:33:23 CEST 2012
CPU: ARMv7 Processor rev 1 (v7I)
CyanogenMod version: 9-20120420-CODEWORKX-galaxys2
Build Date: Fri Apr 20 18:20:53 CEST 2012
Build number: IMM76D