There’s no need to remove the battery. Just disconnect its power socket if you want to be ‘careful’.
I have replaced several Logic boards at this point on the A1304 model, and realized that I did not need to remove the heatsink (Steps 14 through 17). You need to remove the screws around the fan, and disconnect the microphone cable (step 19). Of course if your replacement logic board doesn't include a heatsink, you need to take it off.