I made an account just to vouch for this method. I haven't installed IcEnhancer yet, but my version of GTAIV is running fully with patch 126.96.36.199!
My only recommendation is to make sure you go back into Steam after and RECHANGE the preference to "Do not automatically update this game." otherwise it seems like it changes it back.
After hours of frustrating failure this is such an unbelievable relief! Thank you so much man!