how to upgrade my samsung moment 1.5 to newest upgrade WITHOUT losing the cricket flash

so i spent a good 4 hours with cricket yesterday just so they could properly flash my samsung moment to their carrier. but i realized that my android software is not up to date!
i have been hearing talk that sprint can have you upgrade yourself the 2.1 version, but im afraid that it will take away my flash.
there has been OTHER talks about upgrading it to a 2.2, which is far better, but still can't find it anywhere!
and the LAST thing i searched up is rooting? that if i root my phone first, i can upgrade it however i want and it wont lose my flash.
i am a compete noob, i dont know anything about ANYTHING with phones, or roms, or stuff like that.
can anyone, kindly, help me sort this out? i just want my phone upgraded

 

thank you so much! i thought i didnt post this in the right section! im really new at this!