the slightly higher rpm's will probably keep you running a little slower on the road (ie you wont find yourself cruising at 90mph so much) but thats a good thing.
and YES, get FORD RACING gears. (and supposedly ford motorsport are the same thing). i would definitely pay a few dollars extra for assurance of a factory fit and keeping your rear end warranty.
judging by the installation kit i got from motive (which didnt even get used) they aren't as good of quality as frpp.
my gears cost me just under $400 in the end, not counting calibration.
yes, the MILs are junk, and since the light doesn't go off i did an egr delete as well, the car runs great. and if there is a problem i know what's wrong with the car 90% of the time before the stupid light comes on, if it comes on at all. If there were something wrong i don't need an idiot light to tell me.