MOD 1 pitch on the gears.
and yeh, a fan uses soo little power you wont notice any difference in runtimes.
generally, a heatsink/fan will drop temps 10-15 degrees.
redcat has a heatsink for the 8E's, but not one with a built in fan
if you are gonna gear up, make sure you keep an eye on temps. i think the stock gearing is very good for offroad. for onroad/speed runs you can get away with gearing up without issue.