I installed 12s on my 2012 SESG last May .......ooh bad memories for sure !!!! .....anyway here are my tips :
1-Use 6+ on lines
2-Cover all the bars with blue tape to save from scratches (i learned that the hard way on my previous limited !! )
3-No need to extend wires (just relocate the OEM plug locations) ..although i extended mine ...but was not needed and took lots of time with lots of mistakes
4-Only needed upper brake lines
5-Cover all painted parts with nylon and tape to protect from DOT brake fluid
6-Tank will have to come off for the brake line - no way around it ! (its much easier that it seems , again beware of scratches )
7-Take it easy with the molex connectors -they can break easily
8-Test every thing before you button everything up
9-use lots of lube (i used soap )
10-throttle side is much more difficult , i did left side in 15 mins , right side in 3 hours !!!
get lots of beer , take lots of breaks and enjoy ....lol !
if taking it easy ...12-14 hours and i have been wrenching for 10 years - did everything but engine builds