SP1 is NOT a critical install and can be postponed just make sure your update preferences are not set to automatically install updates.
Your update preferences should be set to Check for updates but let me choose whether to download and install them.
anyway as this allows you to pick and choose at will.
Running the script on a system requires the installation of KB971033 since the script prevents KB971033 from running once installed. After that I believe you can run your choice of loaders.
I have had great success using the combination of the script and w7lxe-loader.
Here is the script and instructions once again;
1. Disconnect from the internet (unplug cable and disable any wireless)
2. Install the leaked update (x86 is for 32-bit, and x64 is for 64-bit)
3. After you install the update and before you restart the computer, go to All Programs -> Accessories and right click on Command Prompt and run it as administrator.
4. Copy, paste and run the following command:
takeown /f "%windir%\System32\Wat\*"
5. After running that command, copy, paste and run the next command:
icacls "%windir%\System32\Wat\*" /deny *S-1-1-0:F
6. Type exit to close the command prompt
7. You are now protected from the update and can reconnect to the internet
Follow the instructions verbatim and there will not be any issues.