Here is the link to more information about ACE. http://www.acefitness.org/getcertified/certification_gfi.aspx
Keep in mind that you will need to be current on CPR/AED as well.
And after you are certified, I recommend lots of continuing education and personal development.
If you are ever coming to the Big Island of Hawaii, consider taking some CECs with me. You can write it off on your taxes as well. (How much depends on how much time you spend taking CECS. How many days with time spent, I believe. But check with your tax guy to be sure.)