You're panicking for nothing. If you set off like 5000 in an hour, that might come up as suspicious as to how you pulled that off, but otherwise, it's not like they're actively looking into it - they don't even actively ban people for visible evidence of modding (e.g. Gears of War 3 developer skins in use by the public). Honestly, if someone reports you, that's probably the only real way you'd be at risk. Otherwise, you're being very, very careful.
They do check but its rarely and just make sure to don't spam like 5000 GS in one day i got my first banned for life because i got some achievements too but it got messed up and changed my reputation and it went to how many years i had gold and idk how they find out i lost all my achievements and many things i made online especially for all the call of duty games and BF3 just try to don't get so many achievements at the same time i just did 2 games completely and that got me banned for life. Thats why i mod everything i can on Xbox just i don't mess around with the gamer tag or gamer score that's how they get people and banned them. Just be very careful with what you mod on xbox.
I had about 30,000 given one day and brought back online the next time I was on and it worked perfect I did half of my achievements at one time. Just always: Better safe then sorry is what I live by
